如图所示，一艘快艇发动机的冷却水箱用一根弯成直角的管子连通到水中，水箱入口处到直角弯管下端的高度差为0. 8m，要使水能流进水箱（不考虑导管对水的阻力），快艇的航行速度至少应达到（g取10m/s²）                       （   ）

A．2.0m/s

B．4.0m/s

C．6. 0m/s

D．8.0m/s

填空题。

(1) experience____

     He would go through fire and water for his country.

(2)look at carefully____

    They went through our luggage(行李)at the

    customs(海关).

(3)look through____

    We spent several days going through all related

    materials(相关材料).

(4)pass through____

    1 was afraid to go through the forest at night.