问题
选择题
| Such a problem still exists because no adequate measures for preventing it _____ taken in the past. |
A. are B. had C. were D. had been. |
答案
答案：C
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| Such a problem still exists because no adequate measures for preventing it _____ taken in the past. |
A. are B. had C. were D. had been. |
答案：C
