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【简答题】
（1）三聚氰胺（化学式为C 3 H 6 N 6 ），是一种重要的化工原料．其中碳、氢、氮三种元素的质量比为 。 （2）制作“叶脉书签”需要100g溶质质量分数为10%的氢氧化钠溶液．请问：若用20%的氢氧化钠溶液和水配制，需要20%的氢氧化钠溶液质量是 g。
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【判断题】E-24标注法有2位有效数字,精度在±2%(-G),±5%(-J) ,±10%(-K) ,±20%(-M);E-96标注法有3位有效数字,精度在±1%(-F)
A.
正确
B.
错误
【单选题】I _______ the dance performance many times, each giving me a new understanding．
A.
watch
B.
watched
C.
have watched
D.
am watching
【单选题】You want to tell me, and I have no objection ______ it.
A.
to hear
B.
to hearing
C.
hearing
D.
having heard
【单选题】--- Why didn’t you tell me the truth that day? --- I _______, but you ______ for Beijing.
A.
would have; left
B.
would; had been away
C.
would have; had left
D.
had; were away
【单选题】You want to tell me, and I have no objection ______ it.
A.
to hear
B.
to hearing
C.
heating
D.
having heard
【单选题】I had considerable difficulty______her to go out for a drink with me.
A.
to persuade
B.
to have persuaded
C.
persuade
D.
persuading
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