However weak your memory may be, you can make up for it by ______ what you want to remember, and repeating it over and over again.

A．gaining access to

B．attending closely to

C．taking advantage of

D．getting the better of

如图所示，质量为m的木块在水平面上的木板上向左滑行，滑行时木板静止，木板质量M=3m，已知木块与木板间、木板与水平面间的动摩擦因数均为μ，则在木块滑行过程中，水平面对木板的摩擦力大小为（　　）

A．4μmg

B．3μmg

C．2μmg

D．μmg