图示单元体中应力单位为MPa，则其最大剪应力为：（） A.60 B.-60 C.20

从方块中选择适当的句子补全下列对话
A; Hello.                                      B: ___小题1:_____
A:_____小题2:_____                               B: Yes， I am.
A : ____小题3:_____                               B: I’m in Class 6
A : ____小题4:_____                               B: I am twelve.
A: Oh，I am twelve too. _____小题5:______           B: Thank you.

A. Please sit on the chair. B. What class are you in ? C. Hello. D. How old are you? E. Are you a new student here?