I’m sure I _____ her four years ago.
A.have seen
B.saw
C.had seen
D.will see
答案:B
夺取北周 * * ,建立隋朝,实现全国统一的是 [ ]
A.杨广
B.李渊
C.杨勇
D.杨坚
压力常用的单位有哪些?如何换算?