两个密度均匀的球体,相距r,它们之间的万有引力为10-8 N,若它们的质量、距离都增加为原来的2倍,则它们间的万有引力为( ) A.10-8 N B.0.25×10-8 N C.4×10-8 N D.10-4 N 答案:A 解析: 原来的万有引力为:F=G后来变为: F′=G=G。 即:F′=F=10-8 N,故选项A正确。
There were fifty people ________ when the accident happened.
[ ]
A.
on the board
B.
on board
C.
board
D.
above board