恒温切冷冻组织切片出现皱褶应调节（）
A.切片速度
B.切片厚度
C.刀刃距离
D.刀的角度
E.防卷板
参考答案：E
— What did she say to you just now?
— She asked me if I knew ____. [ ]
A. whose pen is it
B. whose pen it was
C. whose pen it is
D. whose pen was it
1，4，9，15，18， ( )
A．21
B．24
C．9
D．20
