After a hard ---fought campaign, Barack Obama won the US presidential election, and became

President of the United States---the first African –American in           

country’s history to do so.

A．the; the

B．/; /

C．/; the

D．the; /

我国供食用的牛中质量最好的是（）。

A.黄牛

B.牦牛

C.水牛

D.奶牛