If I hadn't stood under the ladder to catch you when you fel

答案A。wouldn't be smiling
If I hadn't stood under the ladder to catch you when you fell,you (wouldn't be smiling ) now。
翻译：
你掉下来的时候,要不是我站在梯子下面接住了你,你现在就不会这样笑着了。
说明：这是一个虚拟语气的句子,发生的事情在过去,因此前面用hadn't stood,而后面是与现在相反的,所以用wouldn't be smiling