Question

It's nearly eight o'clock．答案为什么是A而不是D？

It's nearly eight o'clock．I must hang up and get down to work．My boss be here at any moment．
A．should B．must C．could D．would
试题答案

Answer 1

should 表示“我老板应当随时会到”。

由于 should 的用法最复杂，英语考试中如果让你从should, would, could 里选一个的话，超过70%的概率是选should.

should 的定义：
1
—used in auxiliary function to express condition <if he should leave his father, his father would die — Genesis 44:22(Revised Standard Version)>
2
—used in auxiliary function to express obligation, propriety, or expediency <'tis commanded I should do so — Shakespeare> <this is as it should be — H. L. Savage> <you should brush your teeth after each meal>
3
—used in auxiliary function to express futurity from a point of view in the past <realized that she should have to do most of her farm work before sunrise — Ellen Glasgow>
4
—used in auxiliary function to express what is probable or expected <with an early start, they should be here by noon>
5
—used in auxiliary function to express a request in a polite manner or to soften direct statement <I should suggest that a guide…is the first essential — L. D. Reddick>

Could的定义相对简单：
—used in auxiliary function in the past <we found we could go>, in the past conditional <we said we would go if we could>, and as an alternative to can suggesting less force or certainty or as a polite form in the present <if you could come we would be pleased>

Would 的定义：

—used to indicate what someone said or thought about what was going to happen or be done
—used to talk about a possible situation that has not happened or that you are imagining
—used with have to talk about something that did not happen or was not done

追问

那为什么不选would？

追答

would作可能是一种不确定的猜测。
而Could则是一种推理，从语意上更适合些。(其实本人也认为WOULD也是可用的。不过中国的应试您懂的。它一定要搞一个“最合适”的。）