DNA is very useful for us, it many years ago. A. discovers B. discovered C. is discovered D. was dis...
2022-11-16 08:37:56 212次 2017届北京通州区九年级上期末考试英语试卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
DNA is very useful for us, it many years ago.
A. discovers
B. discovered
C. is discovered
D. was discovered
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