初级英语,求大师帮忙解释一下为什么要写那个选项
问题描述：
初级英语,求大师帮忙解释一下为什么要写那个选项
“ Mr Brown, why has your company been so slow to act ? ”
“ _____ we known of the problem earlier, we would have acted sooner.”
答
这原本是一个完整的虚拟语气,完整的形式是 If we had known of the problem earlier,we would have acted sooner.把had提前主语放后面是强调句型,所以需要填Had.强调如果我们知道这件事,也就是事实是我们不知道这件事.