无症状的胆囊结石病人，定期复查时，首选的检查方法是

A．B超

B．MRI

C．CT

D．腹部X线平片

E．核素扫描检查

He speaks English _____ an American, so we all think he stays in America for many years. [ ]

A. as good as

B. worse than

C. as badly as

D. as well as