问题
选择题
I personally think__more listening, speaking, reading and writing is the key to__our English.
A．Doing; improve
B．To do; improve
C．Do; improving
D．Doing; improving
答案
答案：D
think后是宾语 从句，且缺少主语，the key to中 to是介词，后面要跟doing形式，而C项Do不能作主语，所以选D。
