首先,这句话的意思是当你被抢劫的时候你会向谁求救?
其次,这句话如果是who would you aks for help if you were robbed?可以看做是一个补语从句,也就是说,去掉 if you were robbed 这句话也成立；前面的who .是一个特殊疑问句,类似于 what are you doing这类常见简单句型.
最后,这句话不能那么改,是个错误的句子.一定要用的话,who应该改成when,不过这时的句意已经和题目的句子发生改变,变为：当你被抢劫时你会求救吗?
希望有所帮助^^