Mike started playing golf when he was 3 years old.A. /B. anC. theD. a

问题补充：

Mike started playing golf when he was 3 years old.

A. /

B. an

C. the

D. a

答案：

(答案→)A. /

B. an

C. the

D. a

解析：根据语境可知此句的含义是Mike在三岁的时候就开始打高尔夫球。play与表示球类的名词连用时不加任何冠词；故选A。