I really can’t thank you enough， sir.    —        .

A．That’s the most I could do

B．I’m glad to have been of help

C．No problem

D．With pleasure

面层、基层和垫层是路面结构的基本层次，为了保证车轮荷载的向下扩散和传递，较下一层应比其上一层的每边宽出( )。

A．0.15m
B．0.25m
C．0.22m
D．0.23m