问题
选择题
| Our teacher told us that pollution _____ a very serious problem in the world we live. |
A. has be B. had been C. is D. was |
答案
答案：C
搜题请搜索小程序“爱下问搜题”
| Our teacher told us that pollution _____ a very serious problem in the world we live. |
A. has be B. had been C. is D. was |
答案：C