Not having a good of English can be a serious disadvantage to achieving your goals.A. pro

问题补充：

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

A. protection

B. appreciation

C. command

D. experience

答案：

A. protection

B. appreciation

(答案→)C. command

D. experience

解析：句意：没有掌握好英语，可能会成为实现你的目标途中的一个严重地劣势。have a good command of是固定用法，意思是精通，选C。