If they knew how difficult it was to drill through the hard rock,they would是虚拟语气吗

题目

If they knew how difficult it was to drill through the hard rock,they would是虚拟语气吗

答案

是虚拟语气,详解如下：
本句子的意思是：如果他们知道钻透那坚硬的岩石有多难,他们就不会.
虚拟语气是说话人为表示一种假设、一种主观的愿望,即动词所表示的动作事实相反（与过去事实、现在事实、将来事实）.
与现在事实相反,从句用if + 主语+动词过去式,主句用 would/ should/ could/ might+动词原形的
本句子是标准的与现在事实相反的情况,
再举例子
If she knew English,she would not ask me for help.
如果她懂英语的话,她不会找我帮忙的.