(1)I don’t know if he ________ or not tomorrow.
此题答案选C,句中if引导的不是条件状语从句(if≠如果),而是宾语从句(if=是否),句意为“我不知道明天他是否会来。”(from www.yygrammar.com)
(2)I don’t know if she ________, but if she ________ I will let you know.
A.comes, comesB.will come, will come
C.comes, will comeD.will come, comes
答案选D,第一个if引导的是宾语从句,第二个if引导的是条件状语从句。
(3)“When he _____ is not known yet.” “But when he ____, he will be warmly welcomed.”
A.comes, comesB.will come, will come
C.comes, will comeD.will come, comes
答案选D,第一个when引导的是主语从句,第二个when引导的是时间状语从句。