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【单选题】
The lack of movement caused the player's muscles to _______ and he might never play the sport again. [ ]A.
hurt
B.
ruin
C.
weaken
D.
threaten
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参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】By '...challenges explanation' (Line 2, Para. 1) the author means that______.
A.
no explanation is necessary for such an obvious phenomenon
B.
no explanation has been made up to now
C.
it's no easy job to provide an adequate explanation
D.
it's high time that an explanation was provided
【简答题】证明：任何两个正交方向的法曲率kn1，kn2之和kn1+kn2为常数．
【简答题】作图示结构的M图。已知P=6kN，q 1 =1kN/m，q 2 =4kN/m，M 1 =12kN·m，M 2 =40kN·m。