Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
I             all of my homework last night.
A.have finished
B.finish 
C.finished 
D. will finish

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
They were among the first companies to exploit the             of the Internet.
A.prospect 
B.ability 
C.potential 
D.possibility

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.
"No, I won't go to work at the weekend," said Sally.
A.Sally apologized for not going to work at the weekend.
B.Sally regretted not going to work at the weekend.
C.Sally promised to go to work at the weekend.
D.Sally refused to go to work at the weekend.

My brother usually ask me for help when he has difficulty with his homework.
A.ask
B.when
C.has
D.homework

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
A university degree is considered to be a                  for entry into most professions.
A.requisite 
B.demand 
C.request
D.claim

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
The      of the Internet has played an important part in the development of communication.
A.research                  
B.invention                 
C.occurrence              
D.display

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
We were                   by the spectacular scenery of the countryside.
A.bewildered  
B.preoccupied  
C.overwhelmed  
D.overjoyed

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

A.reply 
B.answer 
C.future 
D.singer

Mark the letter A, B, C, or D on your answer sheet to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions.

A.watched
B.cleaned
C.missed
D.talked

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 43 to 50.
Earth is richly supplied with different types of living organisms which co-exist in their environments, forming complex, interrelated communities. Living organisms depend on one another for nutrients, shelter, and other benefits. The extinction of one species can set off a chain reaction that affects many other species, particularly if the loss occurs near the bottom of the food chain. For example, the extinction of a particular insect or plant might seem inconsequential. However, there may be fish or small animals that depend on that resource for foodstuffs. The loss can threaten the survival of these creatures and larger predators that prey upon them. Extinction can have a ripple effect that spreads throughout nature.
In addition to its biological consequences, extinction poses a moral dilemma for humans, the only species capable of saving the others. The presence of humans on the planet has affected all other life forms, particularly plants and animals. Human lifestyles have proven to be incompatible with the survival of some other species. Purposeful efforts have been made to eliminate animals that prey on people, livestock, crops, or pose any threat to human livelihoods. Some wild animals have been decimated by human desire for meat, hides, fur, or other body parts with commercial value. Likewise, demand for land, water, and other natural resources has left many wild plants and animals with little to no suitable habitat. Humans have also affected nature by introducing non-native species to local areas and producing pollutants having a negative impact on the environment. The combination of these human-related effects and natural obstacles such as disease or low birthrates has proven to be too much for some species to overcome. They have no chance of survival without human help.
As a result, societies have difficult choices to make about the amount of effort and money they are willing to spend to save imperiled species. Will people accept limits on their property rights, recreational activities, and means of livelihood to save a plant or an animal? Should saving such popular species as whales and dolphins take priority over saving obscure, annoying, or fearful species? Is it the responsibility of humans to save every kind of life form from disappearing, or is extinction an inevitable part of nature, in which the strong survive and the weak perish? These are some difficult questions that people face as they ponder the fate of other species living on this planet.
(Source: http://www.encyclopedia.com)
The word "They" in paragraph 2 refers to                                       .
A.human-related effects      
B.some species
C.natural obstacles   
D.low birthrates