有关虚拟语气的几道题。This kind of world is hard and dangerous.But if__

有关虚拟语气的几道题。
This kind of world is hard and dangerous.But if_____,you would become rich.
a.you would succeed b,you could succeed
c,you might succeed d,you should succeed
请讲明选哪一个，为什么？
_____there be any trouble with the boiler.the automatic controlling unit would cut off the fuel oil supply.
a Would b Must cCould dShould