1.If the book you want is out, you may ask for it to be called back for you, and whether you pay the cost of sending a post card, the librarian will write to you.
解析：此题为五星级题。whether改为If。此题考查if与whether作为连词的区别。此处为if引导的条件状语从句，表示“如果……”；如用whether，则表示“是否”，语意不通。
在下列情况下一般只用whether：引导介词后的宾语从句、主语从句、表语从句、同位语从句或在whether to do, whether…or not…中。
e.g.Whether we’ll go camping tomorrow depends on the weather.
