化简m-n-（m+n）的结果是（ ）
A．0
B．2m
C．-2n
D．2m-2n
原式=m-n-m-n=-2n．故选C．
581年，夺取北周 * * ，建立隋朝的是：（ ）
A．杨坚
B．王莽
C．李渊
D．李世民
①It is the building _____ the goods are stored.
②It is in the building _____ the goods are stored.
③It was midnight _____ we got to the village.
④It was at midnight _____ we got to the village.
A. when
B. that
C. where
D. which
