The question of whether they are male or female is not impor-tant.

　　I have not decided whether to go or not.

　　⑥间接引语位于句首时或者是间接引语提前时用whether不用if。如：

　　Thank you, but whether I'll be free I'm not sure at the moment.

　　⑦whether可引导一个让步状语从句表示"不管"、"无论"，而if不能。如：

　　Whether he comes or not, we will begin our party on time.

（3）疑问词 + ever和no matter + 疑问词的区别。

　　①疑问词 + ever可引导名词性从句，在主从句中要充当一定的部分。如：

　　Whoever breaks the rule must be punished.

　　You can choose whatever you like in the shop.

　　②疑问词 + ever还可引导让步状语从句。如：

　　Whoever breaks the rule, he must be punished,

　　Whatever you do, you must do it well.

③no matter + 疑问词只能引导让步状语从句。如：

　　No matter what you do, you must do it well.

　　No matter who breaks the rule, he must be punished.

（4）when和where引导的同位语从句与定语从句的区别。

when 和where前面的名词若是表示时间、地点的名词，则when和where引导的是定语从句，否则则为同位语从句。如：

　　They put forward the question where they could get the money.

　　This is the place where the accident happened.

　　2、名词性从句中主句和从句的时态一致

（1）宾语从句中主句和从句的时态保持一致，但如果从句中表示提示的是客观现象，虽然主句是过去时态，从句仍用一般现在时。如：

　　Hello,I didn't know you were in London. How long have you been here?

　　The teacher told us that light travels at a very high speed.

（2）主语从句作主语相当于单数第三人称作主语，谓语动词用单数，如果由and 连接两个或两个以上的主语从句作主语时，谓语动词用复数；由两个或多个连接词引导一个主语从句，谓语动词用单数。如：

When the meeting will begin has not been decided yet.