沿长方体三个互不相交且互不平行的棱边分别作用有力 P1、P2、P3，它们的大小均为P，即P1=P2=P3，长方体的尺寸分别用a、b、c表示。当图所示力系P1、P2、P3，能简化为一合力时，长方体的尺寸a、b、c间的关系为()。
A. a=b-c
B. a=c-b
C. a=b+c
D. a=0.5(b+c)
查看答案
The woman in the shop stared at them strangely, because______.
A. they had on funny clothes
B. she saw foreigners for the first time
C. she wondered why they had come into the shop
D. they didn't give her any money
A．Work for a radio station.B．Live in a dormitory.C．Take a long trip.D．Look for another
A. Work for a radio station.
B. Live in a dormitory.
C. Take a long trip.
D. Look for another one.
海关可以行使“径行开验”的权力，即无须任何见证人到场的情况下自行开拆货物，进行查验。()
A. 正确
B. 错误
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