Read the following passage and mark the letter A, B,C, or D on your answer sheet to indicate the correct answer to each of the questions from 51 to 60.
The ability to conduct electricity is one of the key properties of a metal. Other solid materials such as silicon can conduct electricity but only effectively at certain temperatures. Also, some substances such as salt (sodium chloride) can conduct when molten or when dissolved in water. The ability of metals to conduct electricity is due to how their atoms bond together. In order to bond together the metal atoms lose at least one of their outermost electrons. This leaves the metal atoms with a positive charge and they are now strictly ions. The lost electrons are free to move in what is known as a sea of electrons. Since the electrons are negatively charged they attract the ions and this is what keeps the structure together.
An electric current is a flow of charge and since the electrons in the sea of electrons are free to move they can be made to flow in one direction when a source of electrical energy such as a battery is connected to the metal. Hence we have an electric current flowing through the wire, and this is what makes metals such good conductors of electricity. The only other common solid conducting material that pencil users are likely to encounter is graphite (what the ‘lead’ of a pencil is made from). Graphite is a form of carbon and again the carbon atoms bond in such a way that there is a sea of electrons that can be made to flow as an electric current. Likewise, if we have an ionic substance like salt we can make the electrically charged ions flow to create a current but only when those ions are free to move, either when the substance is a liquid or dissolved in water. In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow.
Electrical insulators are substances that cannot conduct electricity well either, because they contain no charged particles or any charged particles they might contain do not flow easily. Water itself is a poor conductor of electricity as it does not contain a significant amount of fully charged particles (the ends of a water molecule are partly charged but overall the molecule is neutral). However, most water we encounter does contain dissolved charged particles, so it will be more conductive than pure water. Many of the problems that occur when touching electrical devices with wet hands result from the ever-present salt that is left on our skin through perspiration and it dissolves in the water to make it more conductive
The word “they” in paragraph 3 refers to ______.




A.charged particles
B.electrical insulators
C.electric currents
D.charged ions

Read the following passage and mark the letter A, B,C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks from 36 to 45.
Why is it that many teenagers have the energy to play computer games until late at night but can't find the energy to get out of bed (36)_______ for school? According to a new report, today's generation of children are in danger of getting so (37)________ sleep that they are putting their mental and physical health at (38)________. Adults can easily survive on seven to eight hours' sleep a night, (39)________ teenagers require nine or ten hours. According to medical experts, one in five youngsters(40)_________ anything between two and five hours' sleep a night less than their parents did at their age. This (41)_________ serious questions about whether lack of sleep is affecting children's ability to
concentrate at school. The connection between sleep deprivation and lapses in memory, impaired reaction time and poor concentration is well (42)_________. Research has shown that losing as little as half an hour's sleep a night can have profound effects (43)________ how children perform the next day. A good night's sleep is also crucial for teenagers because it is while they are asleep (44)________ they release a hormone that is essential for their 'growth spurt' (the period during teenage years when the body grows at a rapid rate). It's true that they can, to some (45)________, catch up on sleep at weekends, but that won't help them when they are dropping off to sleep in class on a Friday afternoon.




A.leve
B.rate
C.extent
D.point

Read the following passage and mark the letter A, B,C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks from 36 to 45.
Why is it that many teenagers have the energy to play computer games until late at night but can't find the energy to get out of bed (36)_______ for school? According to a new report, today's generation of children are in danger of getting so (37)________ sleep that they are putting their mental and physical health at (38)________. Adults can easily survive on seven to eight hours' sleep a night, (39)________ teenagers require nine or ten hours. According to medical experts, one in five youngsters(40)_________ anything between two and five hours' sleep a night less than their parents did at their age. This (41)_________ serious questions about whether lack of sleep is affecting children's ability to
concentrate at school. The connection between sleep deprivation and lapses in memory, impaired reaction time and poor concentration is well (42)_________. Research has shown that losing as little as half an hour's sleep a night can have profound effects (43)________ how children perform the next day. A good night's sleep is also crucial for teenagers because it is while they are asleep (44)________ they release a hormone that is essential for their 'growth spurt' (the period during teenage years when the body grows at a rapid rate). It's true that they can, to some (45)________, catch up on sleep at weekends, but that won't help them when they are dropping off to sleep in class on a Friday afternoon.




A.on
B.IN
C.at
D.to

Read the following passage and mark the letter A, B,C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks from 36 to 45.
Why is it that many teenagers have the energy to play computer games until late at night but can't find the energy to get out of bed (36)_______ for school? According to a new report, today's generation of children are in danger of getting so (37)________ sleep that they are putting their mental and physical health at (38)________. Adults can easily survive on seven to eight hours' sleep a night, (39)________ teenagers require nine or ten hours. According to medical experts, one in five youngsters(40)_________ anything between two and five hours' sleep a night less than their parents did at their age. This (41)_________ serious questions about whether lack of sleep is affecting children's ability to
concentrate at school. The connection between sleep deprivation and lapses in memory, impaired reaction time and poor concentration is well (42)_________. Research has shown that losing as little as half an hour's sleep a night can have profound effects (43)________ how children perform the next day. A good night's sleep is also crucial for teenagers because it is while they are asleep (44)________ they release a hormone that is essential for their 'growth spurt' (the period during teenage years when the body grows at a rapid rate). It's true that they can, to some (45)________, catch up on sleep at weekends, but that won't help them when they are dropping off to sleep in class on a Friday afternoon.




A.A. risk
B.danger
C.threaten
D.threat

Mark the letter A, B, C or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.
We cut down many forests. The Earth becomes hot.




A.The more forests we cut down, the hotter the Earth becomes.
B.The more we cut down forests, the hotter the Earth becomes.
C.The more forests we cut down, the Earth becomes hotter.
D.The more we cut down forests, the Earth becomes hotter.

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
My brother together with my parents..................going to meet my relatives at the airport this afternoon.




A.are
B.were
C.is
D.was

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Tom: “I won the gold medal in the race.”
You: “……………………”




A.Cheers! All the best.
B.That’s all right. Don’t mention it.
C.Well done! I knew you could do it.
D.Good luck! Better luck next time.

Mark the letter A, B, C or D on your answer sheet to indicate the word that differs from the rest in the position of the main stress in each of the following questions.




A.intelligent
B.comfortable
C.necessary
D.secretary

Of all the art-related reference and research library in North America, that of the Metropolitan Museum of Art in New York City is among the largest and most complete.




A.library.
B.that of.
C.among.
D.most complete.

Choose the phrase that best completes the sentence.
The gate is closed to stop the children running into the road.




A.Because the gate is closed, the children can run into the road.
B.They close the gate, and as a result, the children can’t run into the road.
C.The gate is closed so that children can run into the road.
D.In order to keep the children into the road, they close the gate.