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【多选题】
自然界水循环的意义?A.
水质得以净化
B.
水量得以更新再生
C.
维持生态平衡
D.
维持生命繁衍和人类社会发展
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【单选题】(2013·辽宁师范大学附中模拟)Fortunately it happened at night. If the hurricane ________ during the daytime, there ________ more deaths.
A.
had happened; would have been
B.
happened; would be
C.
had happened; would be
D.
happened; would have been
【单选题】Which is NOT a sound argument?
A.
Sabrina wanted to be a better figure skater, so she took extra lessons and practiced every day. Her skating improved so much that she entered a competition.
B.
Yesterday, a black cat ran in front of me, and later, I lost my wallet. If I don’t see that black cat today, I won’t have any bad luck.
C.
We had a storm last night with hurricane-strength winds, and many trees were downed. There was a citywide power outage.
D.
On a clear day, I can see the top of Murphy Monument from my house. If it’s clear tomorrow, I’ll be able to see the monument.
【简答题】霍夫曼重排反应时，当酰胺的a碳有手性，重排后构型（）。（变，不变）
【单选题】发电机定子升不起电压,最直观的现象是( )
A.
定子电压表指示很低或为零;
B.
定子电流表指示很低或为零;
C.
转子电压表指示很低或为零;
D.
转子电流表指示很低或为零。
【简答题】人们通过观察和研究蜻蜓的飞行特点,发明了直升飞机。这体现了认识的()
【简答题】霍夫曼重排反应时,当酰胺的 a 碳有手性,重排后构型____。
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