____ is the small things that can cause serious problems for dormitory relations.
A. That
B. It
C. This
D. The
It was not until ten o'clock ____ he went to bed.
A. when
B. which
C. that
D. how
It was yesterday ____ I met Li Ming at the railway station.
A. when
B. which
C. how
D. that
It was in the street ____ I met him last week.
A. where
B. that
C. who
D. which
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