捆绑起吊时，要合理地选择绑扎点，考虑重心位置。（）
参考答案：对
一列沿x轴传播的简谐横波，其周期为T，某时刻的波形图象如图中的实线所示，再经t=0.2s的波形图如图中的虚线所示．则此列波的波速为多少？
US and allied officials have said they have seen no credible evidence of civilian casualties(伤亡)from the air campaign,and they say that precision weapons are used in the strikes in an effort to （）being hurt.
A．prevent civilians on
B．prevent civilians from
C．Prevent civilians to
D．Prevent civilians in
