
should是shall过去式,但当should本身做一个词的时候不能把它当作shall的过去式;should作独立的情态动词时候没有过去式和过去分词。
It\'s very important to me that you should be there.
你应该到场,这对我很重要。
By that time the new system should be up and running.
到那时这个新系统应该会运转起来了。
Give me one good reason why I should help you.
我为什么要帮你?给我一个充分的理由。