request
1.request不及ask通俗，通常不用在口语里。
2.request在用作名词的时候后面接for，如a request for assistance。但在用作动词的时候是及物动词， 后面不可有for，如He requested assistance里不可在requested后面加上for。
3.request（动词）后面不可接宾语和for，如不可说We requested them for assistance，该改作下面的任何一种表达方式：
- We asked them for assistance.
- We requested assistance from them.
- We requested them to give us assistance.
- We requested that they would give us assistance.（语气比用should婉转）
- We requested that they should give us assistance.
- We requested that they give（虚拟现在式，不用gave）us assistance.
- We requested to be assisted by them.
4.request后面不可接宾语和以that引导的从句，如不可说I requested him that he would help me，该把him删去。
5.说“应某人的请求”在request前面用at。例如：He came at my request.
6.by request作“依照请求”解，request前面不用his, her等词，如She supplied him, by request, with all details of the case和no flowers by request（遵死者遗志不受花圈）。
7.on（或upon）request作“一经请求”解，通常用在商业文件里。例如：
- The book may be obtained (up)on request.
- Copies of the circular are available (up)on request.
- The book will be forwarded free of charge (up)on request.
8.request（名词）后面可以接以that引导的从句，从句里用should或虚拟现在式。例如：His letter contains a request that his aunt should get a room ready for him.和His letter contains a request that his aunt get（不用gets）a room ready for him.把should改作would也可以，语气婉转些。
