词不仅仅是起连接的作用，而且还在从句里担任一定的成分，关系代词常在从句中担任主语、宾语或表语等成分，关系副词常在从句中担任状语，另外在使用上面的这些关系词时，有几个问题值得我们注意首先。
只能用whether而不能用if的情况 1引导主语从句，例如 Whether well make a loan for the project has not been decided 我们是否要为这个项目还没有定下来， OR It has not been
decided whether well make a loan for the
project If well make a loan for the
project has not been decided OR It has not been decided if well make a loan for the project 2作介词的宾语。
例如 I have no idea about whether I can raise the money
for buying a car 我不知道我是否能为买车筹措到资金， I have no idea about if I can raise the money for buying a car 3后接不定式 ，例如 He didnt know whether to go all himself first or wait for her here(正确)他不知道是他自己
