下列急性化脓性腹膜炎的体征中，哪项是错误的 A．全腹压痛及反跳痛 B．腹壁静脉曲张

A 3G mobile phone, _____ to be most useful and fashionable, is popular with some teenagers.[ ]

A. consider

B. considering

C. considered

D. to be considered

—Is that Jack speaking?  

—Sorry, he _______ in. He _______ back in half an hour.       [ ]

A. isn't; will be      

B. wasn't; will      

C. isn't; is    

D. wasn't; was

香港回归以后，《香港特别行政区基本法》取代《英皇制诰》和《皇室训令》，成为香港的现行宪法。

蛋白质的基本组成单位是（）

A.核苷酸

B.核苷

C.肽单元

D.氨基酸

E.肽链