He is going to study hard at math. He wants to be engineer.A. aB. anC. theD. /

问题补充：

He is going to study hard at math. He wants to be engineer.

A. a

B. an

C. the

D. /

答案：

A. a

(答案→)B. an

C. the

D. /

解析：句意：他打算努力学习数学。他想成为一名工程师。a engineer 一名工程师，表示泛指。在可数名词单数的前面要用不定冠词。engineer 并不是元音开头，故不用an；the 表示特指，不符合句意，故选B。