5. Obviously, he ___ a bad cold. He sneezes so often.
A) has
B) has been
C) had
D) was
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6. Darwin proved that natural selection ___ the chief factor in the development ofspecies.
A) has been
B) had been
C) is
D) was
7. While Peggy ___, her brother is playing records.
A) reads
B) is reading
C) has read
D) has been reading
8. It’s been a long time since I ___. How are you?
A) had last seen you
B) saw you last
C) have least seen you
D) last was seeing you
9. We ___ on it for several hours but we have not yet reached any conclusion.
A) work
B) are working
C) have been working
D) have been worked
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