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【单选题】
平面任意力系平衡的充要条件是( )。A.
力系主失等于零
B.
力系合力为零
C.
力系的主失和对于任一点的主矩都等于零
D.
力系对于任一点的主矩都等于零
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举一反三
【单选题】— When is your birthday? — My birthday is ________. [ ]
A.
June second
B.
June two
C.
second June
D.
two June
【单选题】When was McVeigh executed?
A.
in April 1995.
B.
In June 1995.
C.
In June 2001.
D.
In June 2002.
【简答题】A．First Sunday in June. B．Second Sunday in June. C．Third Sunday in June. D．Decided by each President.
【单选题】某校开设5门不同的数学选修课，每位同学可以从中任选1门或2门课学习，甲、乙、丙三位同学选择的课没有一门是相同的，则不同的选法共有（ ）
A.
330
B.
420
C.
510
D.
600
相关题目：
【单选题】When was McVeigh executed?
A.
in April 1995.
B.
In June 1995.
C.
In June 2001.
D.
In June 2002.