If they knew how difficult it was to drill through the hard rock,they would是虚拟语气吗
问题描述：
If they knew how difficult it was to drill through the hard rock,they would是虚拟语气吗
答
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.