今天小编为大家分享生活中的小常识、日常问题解答等相关内容,希望能够帮助大家。1、If the clause: completed2、Main sentence: Modal verbs (will, may, may, should) have been done.3、If the clause: past/ever4、Main sentence: modal verbs (will, may, may, should) do.5、If the clause: should/should be done