已知月球的质量是7.3×10²²kg，半径是1.7×10³km，月球表面的自由落体加速度有多大？（G=6.67×10^-11N•m²/kg²）

A sea anchor is（）.

A.a heavy anchor with an extra long line used to anchor in deep water

B.a cone shaped bag used to slow down the wind drift effect

C.a padeye to which the sea painter is made fast

D.made of wood if it is of an approved type