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【判断题】
发动机采用4气门和5气门方案可以增加进、排气流动面积,减少流动阻力损失。对于汽油发动机,还可以中置火花塞,缩短火焰传播距离,提高发动机的抗爆性。A.
正确
B.
错误
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【单选题】The two men had hardly had time to ________what had happened when they were thrown violently into the sea.
A.
recognize
B.
realize
C.
understand
D.
grasp
【简答题】B. Fill in each blank with a proper temporal conjunction ( 用时间连词填空 ) 。 After Once when until soon after 1. They kept on working it because completely dark. 2. They had hardly started to work the ...
【简答题】车载局域网主要由 、 、 、 和网关构成。
【单选题】Hardly ______ when the door suddenly closed.
A.
they had arrived
B.
they arrived
C.
did they arrive
D.
had they arrived
【单选题】If they had worked hardly, they die project ahead of time.
A.
will finish
B.
would have finished
C.
have finished
D.
had finished
【单选题】下列说法不正确的是（）
A.
酰氯和酸酐都可以作为Friedel-Crafts酰基化试剂
B.
Friedel-Crafts烷基化反应中AlCl3,ZnCl2,H3PO4,H2SO4是常用催化剂
C.
卤代烃，烯烃和醇都可以用作Friedel-Crafts烷基化的烷基化试剂
D.
Friedel-Crafts反应是典型的自由基反应
【单选题】Many developed countries have agreed to help the less developed ones but it remains ________ whether they will take action or not.
A.
to see
B.
to be seen
C.
seeing
D.
seen
【简答题】羟乙基化试剂是 A. 卤代烃 B. 环氧乙烷 C. 硫酸二乙酯 D. 芳磺酸酯 2 .常用于制备联芳胺的反应是 A. 乌尔曼反应 B. Friedel -Crafts 反应 C. Dele′pine 反应 D. Gabriel 反应 3 . Williamson 反应的产物是 A. 烃类 B. 酰胺类 C. 酯类 D. 醚类 4 .羰基化合物 α 位 C- 烃化的反应条件是 A. 碱性 B. 酸性...
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