They kept trying, and their efforts finally _______.

A．make it

B．paid off

C．are made it

D．are paid off

排土场滑坡类型分为排土场内部滑坡、沿排土场与基底接触面的滑坡和沿基底软弱面的滑坡。当排土场的基底倾角较陡，排土场物料本身的抗剪强度大于排土场与基底接触面之间的抗剪强度时，可能导致( )。

A．排土场泥石流
B．沿基底软弱面的滑坡
C．排土场与基底接触面的滑坡
D．排土场内部滑坡