问题
选择题
_____ many times, John still couldn't work out the problem. [ ]
A. Trying
B. Tried
C. To try
D. Having tried
答案
答案：D
搜题请搜索小程序“爱下问搜题”
_____ many times, John still couldn't work out the problem. [ ]
A. Trying
B. Tried
C. To try
D. Having tried
答案：D