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举一反三
【单选题】A Frenchman (法国人) once came (来，出现) to London to study. He lived at his friend’s home. He worked very hard (41) his lessons. Every morning, he often (42) reading by the window. His friend, John, liked...
A.
is
B.
said
C.
means
【单选题】下列碳正离子的最稳定的为 ( )
A.
CH 3 CH 2 +
B.
C 6 H 5 CH 2 +
C.
(CH 3 ) 2 C + H
D.
(CH 3 ) 3 C +
【单选题】下列关于撞击吸收结构的描述中，哪项说法是不正确地？（）
A.
它有效地将撞击能量集中到乘员舱
B.
它有效的分散乘员舱上的撞击能量
C.
它靠吸收撞击能量来降低减速度
D.
前后侧梁上均有能量吸收区域