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Directions: Beneath each of the following sentences there are four choices marked A, B, C and D. Choose the one answer that best completes the sentence.
21. In the past two decades, research our knowledge about sleep and dreams.
A. expanded B. has expanded C. expands D. has been expanded
22. The number of in our class fifty.
A. student; isB. the students; isC. the student; areD. students; are
21. In the past two decades, research our knowledge about sleep and dreams.
A. expanded B. has expanded C. expands D. has been expanded
22. The number of in our class fifty.
A. student; isB. the students; isC. the student; areD. students; are
