I supported him in time,otherwise he would have fallen off the brink.A might fall B would fall C would have fallen D should have fallen为什么不选B?从句是一般过去式,主句应用would+原形,

I supported him in time,otherwise he would have fallen off the brink.A might fall B would fall C would have fallen D should have fallen为什么不选B?从句是一般过去式,主句应用would+原形,
I supported him in time,otherwise he would have fallen off the brink.
A might fall B would fall C would have fallen D should have fallen
为什么不选B?从句是一般过去式,主句应用would+原形,

I supported him in time,otherwise he would have fallen off the brink.A might fall B would fall C would have fallen D should have fallen为什么不选B?从句是一般过去式,主句应用would+原形,
这是虚拟语气的用法.对过去的动作的虚拟用 would have done的形式.本句子叙述的是过去的事.所以用C would have fallen

是虚拟语气，不是没倒嘛

主句是I supported him in time，是一般过去式
would have fallen 是对过去的虚拟
意为：要不是我支撑着他（过去），他早就掉落边缘了（在我支撑他之前）