在成型复杂塑件时,为了方便凹模的加工、减小热处理变形和节省模具贵重材料,可把凹模做成组合形式。
参考答案:对
---Look! The light is still on. Is Mr Wu working in his office?
---No, it _____ be Mr Wu. He has gone to Nanjing for a meeting.
A.needn’t
B.mustn’t
C.can’t
D.wouldn’t
下列各式中一定为负数的是( )
A.-(-2)
B.-(-2)3
C.-|-2|
D.(-3)2