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问题
单项选择题
脱乙烷塔的重关键组分是()。
A.H
2
B.甲烷
C.乙烯
D.乙烷
E.丙烯
答案
参考答案:E
填空题
一元二次方程x(x﹣3)=2(x﹣3)的根是
_________
.
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选择题
Mother's Day will come soon. Why _______ some flowers for your mother?
A. not to buy
B. not buy
C. don't buy
D. to not buy
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