Question

otherwise but for without 虚拟时用法

Answer 1

otherwise ： 用otherwise的虚拟条件句中，前一部分是陈述语气，后一部分是虚拟语气。
如：I ran all the way to school , otherwise I would have been late .
我一路跑到学校，不然就迟到了
but for : 有时虚拟语气可用but for , without , under 等介词短语引导。这个没特别的规律用法。
如：But for electricity (=If there were no electricity ) , there would be no modern industry.
要是没电，就不会又现代工业。

Answer 2

otherwise but for without
without, otherwise, but for, but引导的短语或句子有时相当于一个虚拟条件句。假设的情况并不以条件从句表示出来,而是暗含在上下文中,通过介词短语来表示.
使用到这些词组的句子中，虚拟语气的用法一般是：对现在的虚拟：would+do；对过去的虚拟：would(not) + have done。

比如：But for your reasonable advice,i wouldn't have fininshed my paper excellently.Without bring in him as the PM(project manager项目经理)of our company,the important program would have failed.
I should study more hard,otherwise i would have kepet with the most outstanding sutdent in my class in last exam. Your mother would go with you,but she has to take care of your elder brother