Not having a good of English can be a serious barrier to achieving your goals.A. demandB.

问题补充：

Not having a good of English can be a serious barrier to achieving your goals.

A. demand

B. appreciation

C. command

D. experience

答案：

A. demand

B. appreciation

(答案→)C. command

D. experience

解析：

这题考查固定词组：having a good command of“精通”，句意是：不能精通英语可能是你取得成功的严重的障碍。选C。