1.以下选自文章 a student in economics
I couldn'twork fewer hours and stay in school, sir. I just barely get by as it is. Iget my board at The Wigwam, and I pay my room rent, and I've been paying out ona suit of clothes. That leaves only about a dollar a week for all the otherthings I have to have.
Can't you arrange for a little financial support fromhome?
No, sir, I'mafraid I couldn't. I have two brothers and two sisters at home younger thanI am. It wouldn't be right for me toask my father to send money out of what he makes.
粗体都是虚拟语气，所以平时对话中是否单独出现一句过去时态的句子，就大概是表示虚拟语气？
2. If you flunk out, the university authorities areobliged to see that you return to your home immediately.
夏济安评：“这里youreturn的return也是虚拟语气；倘若主语是he或she，return也不需要加s。”为何主语是he,return也不加s呢？
3. see that引导的从句也可以用一般目前时来代替以后时，这样的情况就不是虚拟语气了吗？
4. 虚拟语气就是倒退一个时态来表示虚拟的吗？
1 二个couldn't不是虚拟语气，而是用情态动词的过去形式表示委婉。wouldn't be right可以理解为虚拟语气，由于句子暗示说话人不会作不定式表示的这个动作，等于 If I asked... it wouldn't be right. 即不定式短语等于一个虚拟条件，表示以后不可能发生的事。
2、3 see to it that后的从句不需要虚拟语气，而是用一般目前时表示以后，用一般过去时表示过去以后。这个that从句的内容是说话人觉得必须要发生的事情，说话人把that从句所说的事当做以后事实对待的。所以这里要用陈述语气。因为从句内容不牵扯说话人的预测，也不牵涉that从句主语的意愿，所以that从句也没理由用情态动词will或would. 在实质应用中，非正式语体有用will/would的，但标准的句型应该是从句用一般目前时（主句为目前时间）或一般过去时（主句为过去时间）。
4 虚拟语气包含目前式虚拟语气和过去式虚拟语气二个种类。前者用动词原型，后者才是你所说的所谓”退一格“。