坝体碾压应采用振动平碾，其工作重量不小于( )。
A．10t
B．15t
C．20t
D．25t
参考答案：A
— It's been six weeks________he made a misunderstanding of me.
— Don't worry.He's just too busy.[ ]
A. since
B. before
C. when
D. that
DF7D型内燃机车的自重为（）t。
A.127
B.128
C.130
D.131
