He asked her to marry him and she ______. He was very happy to jump into the air.          [ ]

A. received                        

B. accept          

C. didn't                          

D. accepted

如图所示，倾角为θ的斜面上有一质量为m的物体，在水平推力F的作用下移动了距离s，如果物体与斜面间的动摩擦因数为μ，则推力所做的功为（　　）

A．Fssinθ

B．Fscosθ

C．μmgscosθ

D．mg（sinθ+μcosθ）s