6. It was difficult to guess what her ________ to the news would be.
A. impression
B. reaction
C. comment
D. opinion
7. ______ is known to the world, Mark Twain is a great American writer.
A. That
B. Which
C. As
D. It
8. Evidence came up ______ specific speech sounds are recognized by babies as young as 6 months old.
A. what
B. which
C. that
D. whose
9. The robots used in nuclear power plants can prevent human personnel from being ______ to radiation.
A. released
B. disclosed
C. revealed
D. exposed
10.________, they began to get down to business.
A. The holidays are over
B. The holidays were over
C. The holidays being over
D. The holidays had been over
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