They elected Lincoln president of the United States.A. aB. anC. theD. /

问题补充：

They elected Lincoln president of the United States.

A. a

B. an

C. the

D. /

答案：

A. a

B. an

C. the

(答案→)D. /

解析：表示官衔、职位的名词前不用冠词。