All of us think _______ necessary to take exercise every day.
A. this
B. that
C. it
D. them
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More than ________ of the students in our class ________ money to the disabled these days.
A. sixty percent; have donated
B. sixty percents; have donated
C. sixty percent; has donated
D. sixty percents; has donated
This author's third novel ________ in 2018.
A. is published
B. had published
C. was published
D. published
He didn't leave the office ________ his boss came back.
A. when
B. until
C. if
D. as
Generally, air will be heavily polluted ___________ there are factories.
A. what
B. that
C. which
D. where
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