The bell rang the teacher was explaining the experiment to the students.
A. until
B. before
C. while
D. after
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Now most families have only one child our country's one-child policy.
A. so
B. because
C. because for
D. because of
Pandas are facing danger! The situation won't change humans stop killing.
A. unless
B. though
C. if
D. after
-- Can't I park my car free here?-- You can, for four hours, you spend over 100 yuan in this supermarket.
A. though
B. if
C. unless
Mike didn't win the race , he was still wearing a smile on his face.
A. If
B. Since
C. Although
D. Because