How should I know where Betty lives?
l don't know why you should think that l did it .(我真不知道你凭什么认为这件事是我干的。)
e. 情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。如：
I should think it would be better to try again．(我倒是认为最好再试一试。)
You are mistaken，I should say．(依我看，你是搞错了。) I should advise you not to do that．(我倒是劝你别这样做。)
This is something l should have liked to ask you．(这是我本来想问你的。)
f. 虚拟语气， 在主语从句中，“竟然”
It is strange that you should forget his name.（竟然）
If it should rain tomorrow, we would have to stay at home.(Should it rain tomorrow)（万一）
g. should还可以用在if引导的条件从句中，表示一件事听起来可能性很小，但也不是完全没有可能。
相当于\万一\的意思。从句谓语由should加动词原形构成，主句却不一定用虚拟语气。如：
Ask her to ring me up if you
should see her．(你万一见到她，请让她给我打个电话。) If you should change your mind，please let us know．(万一你改变主意，请通知我们。) 在if引导的虚拟条件句中，如果条件状语从句位于句首，且从句中含有should，则可以省略if，并用倒装结构。
Should you change your mind, do let me know. =If you should change your
