John plays the piano _____, if not better than, David. But he never shows off in public.

A．as well

B．as well as

C．so well

D．so well as

起动汽油发动机时，无着火征兆，检查油路，故障是（）。

A、混合气浓

B、混合气稀

C、不来油

D、来油不畅