Both if and whether are used in reporting questions which expect 'yes' or 'no' as the answer * if 和 whether 均用于要求以 yes 或 no 作答的转述疑问句中：◆She asked if/whether I wanted a drink.她问我要不要喝点什么。 although whether sounds more natural with particular verbs such as discuss, consider and decide. When a choice is offered between alternatives, if or whether can be used.不过 whether 与 discuss、consider 和 decide 等动词连用听起来更自然。提供选择时用 if 或 whether 均可：◆We didn't know if/whether we should write or phone.我们不知道是写信好还是打电话好。 In this last type of sentence, whether is usually considered more formal and more suitable for written English.在最后这一句型中，一般认为 whether 较正式，更适用于书面语。