A:what; which
B:what ;what
C:which; which
D:which; what
7+8=____,15-7=____,15-8=____
1233 ____
如图所示,固定斜面倾角为θ,一个物体在与斜面平行的拉力F作用下,沿斜面向上运动一段距离L.在此过程中,拉力F对物块做的功为( )