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【简答题】
瞬心是作相对运动两构件的瞬时 ________ 重合点。如果两构件之一是静止的,则其瞬心是 _________ ;如果两构件都是运动的,则其瞬心是 __________ 。
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举一反三
【单选题】—Must I leave the room now? —No, you . [ ]
A.
needn't
B.
can't
C.
mustn't
D.
couldn't
【简答题】流行性脑脊髓膜炎可用哪些药物作抗菌治疗？为什么？
【单选题】-May we leave the classroom now? -No, you _______. You _______ to leave until the bell rings.
A.
can't; are allowed
B.
mustn't; aren't allowed
C.
needn't; are allowed
D.
needn't; aren't allowed
【单选题】听力原文：The James were supposed to leave in the afternoon, but they couldn't get away until evening. When did the James leave?
A.
The James left that afternoon.
B.
The James didn't get away until afternoon.
C.
The James left in the evening.
D.
The James were supposed to leave in the evening.
【简答题】A．He can't leave his room. B．His homework should be done on time. C．He can't go shopping. D．His daily actions are limited.
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