It can be inferred from the first paragraph that _______.
A.water vapor is an air pollutant in localized areas
B.most air pollutants today can be seen or smelled
C.the definition of air pollution will continue to change
D.a substance becomes an air pollutant only in cities

For which of the following reasons can natural pollutants play an important role in controlling air pollution?
A.They function as part of a purification process.
B.They occur in greater quantities than other pollutants.
C.They are less harmful to living beings than other pollutants.
D.They have existed since the Earth developed.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
Tennis fans _____ tickets have been queuing all night at Wimbledon.
A.who are hoped to buy
B.whom hoped to buy
C.hoping to buy
D.hoped to buy

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
Ann pretended ______ me as he passed me in the street.
A.not seeing
B.not to seen
C.not see
D.not to see

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
I have just bought a television set _ _ in Japan.
A.which made
B.in which made
C.who is made
D.made

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
He is a very intelligent boy; _________, he sometimes gets bad marks.
A.otherwise
B.thus
C.so
D.however

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
__________ in the 19th century, my house is the oldest one in the village.
A.It was built
B.Built
C.On building
D.Building

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
I remember ___________ this phone on my 10th birthday.
A.to be given
B.being given
C.to have given
D.having given

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
Scientists now understand ____________.
A.how birds navigate over long distances
B.how to navigate over long distances the birds
C.how to distance the birds from navigating
D.how long distances navigate the birds

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
__________he followed my advice, he__________ be unemployed now.
A.Unless/ can’t
B.Should/ will
C.Were/ would not
D.Had/ would not