所谓“刚体平动”，指的是刚体运动时有下列( )项特性。
A. ( 刚体内有一直线始终保持与它原来的位置平行
B. ( 刚体内有无数条直线始终保持与它原来的位置平行
C. ( 刚体内任一直线始终保持与它原来的位置平行
D. ( 某瞬时，刚体内各点的速度相同
查看答案
一截面面积突然扩大的圆管，细管直径为15cm，粗管直径为30cm，当管内水的流量为0.22m3/s时，截面突然扩大处的局部损失为（）。
A. 1.48mH2O
B. 1.98mH2O
C. 3.95mH2O
D. 4.44mH20
The defense minister promised to keep the president __________ of the situation in the Middle East.
A. being informed
B. informed
C. to be informed
D. informing
纳税人用于公益、救济性的捐赠，在年度应纳税所得额( )以内的部分，准予扣除。
A. 1.5%
B. 2%
C. 3%
D. 14%
Which of the following statements is true
A. Families worked in loosely organized groups.
B. Land was distributed to each member in a family.
C. The family was the smallest unit in westward migration.
D. Families moved westward to seek religious freedom.
微信支付 
支付宝支付