he went to Australia to study English.A. When a boy of 12B. He was 12 years oldC. When h

问题补充：

, he went to Australia to study English.

A. When a boy of 12

B. He was 12 years old

C. When he was the age of 12

D. When was 12

答案：

(答案→)A. When a boy of 12

B. He was 12 years old

C. When he was the age of 12

D. When was 12

解析：考查省略。当主句和从句的主语一致，而从句又是主语+be动词的形式，这时从句的主语和be动词可以省略。故When a boy of 12 = When he was a boy of 12，故选A。