Do you often ride bike to school Tom?No. I usually come to school by bus.A. a

问题补充：

--- Do you often ride bike to school, Tom?

--- No. I usually come to school by bus.

A. a, a

B. a, the

C. /, /

D. a, /

答案：

A. a, a

B. a, the

C. /, /

(答案→)D. a, /

解析：句意：你经常骑自行车去学校吗？汤姆。——不，我通常成公交车来学校。结合语境可知上文指的是骑任何一辆自行车，故用不定冠词。下文by在表示交通方式时，后面直接接交通工具，故选D。