机械行业中的坍塌事故不包括( )。

A．爆破引起的坍塌

B．堆置物倒塌

C．挖沟时的土石塌方

D．建筑物坍塌

What’s the speaker going to do with the letter

A．He would throw it away.

B．He would keep it.

C．He would post it.

D．He would stick a stamp on it.