逍遥学能 2018-11-15 15:34
①宾语从句是否定句时,只用if,不用whether。
e.g. I wonder if it doesn’t rain.
②用if 会引起误解,就要用whether。
e.g. Please let me know whether you want to go(此句如果把whether改成if,容易当成条件句)
③宾语从句中的whether 与or not直接连用,就不能换成if;不直接连用,可换。
e.g. I don’t know whether or not the report is true. I don’t know whether/ if the report is true or not.
④介词后的宾语从句要用whether引导。whether 可与不定式连用。whether也可引导主语从句、表语从句、同位语从句,还可引导让步状语从句,以上均不能换成if。但引导条件从句时,只能用if,而不能用whether。
e.g. It depends on whether we have enough time. They don’t know whether to go there. Please come to see me if you have time.
注意:在demand、order、suggest、decide、insist, desire, request, command, doubt等表示要求、命令、建议、决定等意义的动词后,宾语从句常用“(should)+ 动词原形”。
e.g.I insist that she (should) do her work alone. 我坚持要她自己工作。
The commander ordered that troops (should) set off at once. 司令员命令部队马上出发。