Subjunctive mood
(1) Nevertheless, should a fight follow, neither creature will be badly hurt, for the loser will save himself by making
a gesture of submission. (Line 5)
(2) If it had not had this disability it would have undoubtedly stayed in the jungle and hunted for food in the customary way. (Line12)
If the human population had not increased so rapidly, people would have had more space and freedom. (Line 23)
(3) If the caged lion, for example, were free to wander on the grassy plains of Africa, it would be continually active, ranging over long distances, hunting in family groups. (Line 15)
此三类句子体现了虚拟语气的三种时态变化。
（1）第1句中“should a fight follow”是表示将来情况的虚拟语气，意思为“if a fight should follow”，句中省略了“if”，将“should”提前，构成倒装，表示“万一，一旦”的意思。值得注意的是本句中的主句部分未使用虚拟语气。
(2) 第二部分这两句是与过去事实相反的虚拟语气。这类句子，从句用“had +动词过去分词”，主句用“would/should/could/might + have + 动词过去分词”。
(3) 第3句是与现在事实相反的虚拟语气。从句用“did/were”，主句用“would/should/could/ might + 动词原型”。
虚拟语气专项复习：
A．虚拟语气在非真实条件状语从句中的用法
1、表示与现在事实相反的情况：
if+主语+过去时+其他+主语+should/would/could/might+do+其他
例：If I were you, I would take an umbrella.如果我是你，我会带把伞。
If I knew his telephone number, I would tell you. 如果我知道他的电话号码，我就会告诉你。
If there were no air or water, there would be no living things on the earth.
If I had any money with me, I could lend you some. 如果我带钱了，我就会借给你些。（事实：没带钱）If he studied harder, he might pass the exam.如果他再努力些，就能通过考试了。（事实：学习不用功）2、表示与过去事实相反的情况
if+主语+had done +其他+主语+should/would/could/might+have done+其他
例：If I had got there earlier, I should/could have met her. 如果我早到那儿，我就会见到她。
If he had taken my advice, he would not have made such a mistake.
3、表示对将来情况的主观推测
①if+主语+did/should/were to do+sth.+主语+should/would/could/might+do+其他
② if+主语+did/be(were)+sth.+主语+should/would/could/might+do+其他
③if+主语+should+do+sth.+主语+should/would/could/might+do+其他
例：If he should come here tomorrow, I should/would talk to him. 如果他哪天来这儿的话，我就跟他谈谈。
If there were a heavy snow next Sunday, we would not go skating.
If she were to be there next Monday, I would tell her about the matter.
4、有时，虚拟条件句中，结果主句和条件从句的谓语动作不是同时发生时，
①从句的动作与过去事实相反，而主句的动作与现在或现在正在发生的事实不符。
如：If I had worked hard at school, I would be an engineer, too. 如果我在学校学习刻苦的话，我现在也会成为一个工程师了
If they had informed us, we would not come here now. 如果他们通知过我们的话，我们现在就不会来这里了。
②从句的动作与现在事实相反，而主句的动作与过去事实不符。如：
If he were free today, we would have sent him to Beijing. 如果他今天有空，我们会已经派他去北京了。
If he knew her, he would have greeted her. 要是他认识她的话，他肯定会去问候她了。
③从句的动作与过去发生的情况相反，而主句的动作与现在正在发生的情况相反。如：
If it had not been raining too much, the crops would be growing much better. 如果天不下太多的雨的话，庄稼会长得更好。
If he had been working hard, he would be working in the office now. 要是他一直努力工作的话，他现在已进了办公室了。
5、当虚拟条件句的谓语动词含有were, should, had时，if可以省略，这时条件从句要用倒装语序，即将were, should, had等词置于句首，这种多用于书面语。如：
Should he agree to go there, we would send him there. 要是他答应去的话，我们就派他去。
Were she here, she would agree with us. 如果她在这儿的话，她会同意我们的。
Had he learnt about computers, we would have hired him to work here.
6、非真实条件句中的条件从句有时不表达出来，只暗含在副词、介词短语、上下文或其他方式表示出来，这种句子叫做含蓄条件句，在多数情况下，条件会暗含在短语中，如without…., but for….等But for his help, we would be working now. 要不是他的帮助，我们还会在工作呢。
Without your instruction, I would not have made such great progress. 要是没有你的指导，我不会取得如此大的进步。
We didn’t know his telephone number; otherwise we would have telephoned him. 我们不知道他的电话号码，否则我们就会给他打电话。
7、有时，虚拟条件句中，主、从句可以省略其中的一个，来表示说话人的一种强烈的感情。
①省略从句
He would have finished it. 他本该完成了。
You could have passed this exam. 你应该能通过这次考试了。
②省略主句
If I were at home now. 要是我现在在家里该多好啊。
If only I had got it. 要是我得到它了该多好啊。
B. 虚拟语气（Subjunctive Mood)的其他用法
1、虚拟语气用在wish 后的宾语从句
a、表示与现在事实相反的愿望，谓语动词用过去式
eg. I wish I had your brains.我希望我有你那样的头脑。(事实：我根本比不上你)
b、表示与过去事实相反的愿望，谓语动词：had+done(动词过去分词）
eg:.I wish I had known the truth of the matter.我希望我原来知道这件事的真相。（事实：原来不知道）
c、表示将来难以实现的愿望
谓语动词：should/would + 动词原形
eg. I wish I should have a chance again.我希望还能有一次这样的机会。（事实：很难再有这样的机会了）(注：if only和as if/as though也有相同用法）
2、虚拟语气用在目的状语从句中
