a pressing suggestion =ought to"应该"
We should/ought to learn about the computer and make full use of it.
You are his father. You ought to take care of him.你是他父亲，你应当照顾他
（当表示道义上的责任义务时，只能用ought to）
可表说话人的感情：amazed;surprised惊奇/anger愤怒/disappointed失望
Why should I go?我干嘛要去（表示不满）
I was shocked that she should have said such a thing to you.(表惊奇)
Possibility:
1. 表推测 可能时，往往有一定根据，含“按道理应该”之意
2. should作情态动词, 用在so that/for fear that/lest引导的目的状从； in case (that)引导的条件状从中，有“可能、将会”之意
They should be at home by now for they have been away for 2 hours.
They got up early so that they should(=could/might) catch the first bus in time.
He is working hard for fear that he (should) fall behind others.
He took an umbrella in case (that) it (should) rain.
用在suggest/propose/arragne/plan/decide/advice/order/demand/request/desire/insist等表示“建议/要求/命令/决定/安排/计划/主张”的动词后+宾从, should可省, 表a tough tone for emphasis强硬语气引起重视
He suggested/demanded/advised that they (should) read the rules carefully.
He insisted that we (should) take up the matter at the meeting.
用在"It is desired/suggested.requested/ordered/proposed/decided"后+定从should也可省
It has been planned that they (should) leave the following week.
It has been decided that the meeting (should) be postponed till tomorrow.
用在"It is/was necessary/important/strange/incredible"或
“It is a pity/ a shame/ no wonder"后+主从
It is necessary that he (should) be sent there at once.
It is a great pity/shame that he should be so conceited.
用在suggestion/motion/proposal/order/plan/idea/advice/
request/decision/requirement后+表从/同位语从句，should可省
My idea/motion/advice is that we (should) do more exercises every day.
We all agreed to his suggestion/proposal that we (should) go to Nanjing for a visit. (同位语从句)
