By the time he was 50 he had become president of company.A. / anB. / a C. a an D. a t

问题补充：

By the time he was 50, he had become president of company.

A. /, an

B. /, a

C. a, an

D. a, the

答案：

A. /, an

(答案→)B. /, a

C. a, an

D. a, the

解析：考查冠词。英语当中一些表示独一无二的职位的名词作表语或者补语的时候，单独使用，不需要加冠词。所以第一空不填。第二空后的company是一个单数可数名词在题中是泛指一家公司。