如图所示，叠放的物块A、B一起沿斜面C匀速下滑，C在粗糙水平面上仍能保持静止（A、B的上下表面均与斜面平行）．已知A、B、C的质量分别为m₁、m₂、m₃，A、B间的动摩擦因数为μ₁，B、C间的动摩擦因数为μ₂，则（　　）

A．B给A有沿斜面向上的静摩擦力，大小等于μ₂ m₁gcosθ

B．B给C有沿斜面向下的滑动摩擦力，大小等于（m₁+m₂） gsinθ

C．B给C的作用力竖直向下，大小等于（m₁+m₂） g

D．地面给C的弹力大小等于（m₁+m₂+m₃） g，地面给C的摩擦力水平向左

Anchor shackles should have a breaking strength that is（）.

A.equal to the chains they are connecting

B.25% more than the chains they are connecting

C.50% more than the chains they are connecting

D.100% more than the chains they are connecting