(1)應(yīng)當(dāng)，應(yīng)該(表示責(zé)任或義務(wù))(used to express duty or moral obligation)：Every citizen～to help/obey the law.每一個(gè)公民都應(yīng)該提供幫助/遵紀(jì)守法。Teachers～to be honoured.教師應(yīng)該受到尊重。I～not to go on living this way.我不應(yīng)該再這樣生活下去了。
(2)(本)應(yīng)該(表示勸告或推薦)(used to express advice or recommendation)：You～not to have spoken to her in that way.你本不該那樣跟她講話。You～to have had more consideration for her.你本應(yīng)該多體諒她。
(3)想必，照說(shuō)應(yīng)該(表示揣測(cè))(used to express possibility or natural consequence)：It～to be ready by now.到現(xiàn)在照說(shuō)應(yīng)該準(zhǔn)備好了。That～to be the postman.那想必是郵遞員。If he had started at nine o'clock，he～to have been in London by eleven o'clock.如果他9點(diǎn)出發(fā)，到11點(diǎn)時(shí)就應(yīng)該已經(jīng)到倫敦了。