—Are you pleased with what he has done?

—It couldn’t be____. Why didn’t he put more effort into his work?

A．any worse

B．much better

C．so bad

D．the best

（）的PDH信号是无法复用成STM-N信号的。

A.2Mbit/s

B.34Mbit/s

C.140Mbit/s

D.8Mbit/s