根据句意，用括号中所给单词的正确形式填空，每空一词。

小题1:Many fans felt sad because of the     (lose) of the famous Korean actor.

小题2:Lucy often plays tennis to relax     (she) after school.

小题3:Thanks to these     (science) work, our dream has become true.

小题4:The patient has difficulty     (run) on his own feet.

小题5:We tried to stop the fights, but we knew it was     (hope).

用轻弹簧竖直悬挂质量为m的物体，静止时弹簧伸长量为L₀，现用该弹簧沿斜面方向拉住质量为2m的物体，系统静止时弹簧伸长量也为L₀，斜面倾角为30°，如图所示。则物体所受摩擦力

A.等于零

B.大小为，方向沿斜面向下

C.大小为，方向沿斜面向上

D.大小为mg，方向沿斜面向上