由 whether 和 if 引导的宾语从句

* Nobody knows whether (if) it will rain tomorrow. 没有人知道明天是否下雨。
* The old woman asked me if (whether) I knew the way to the hospital. 老妇人问我是否知道去医院的路。
* Tom asked if (whether) I had read the book. 汤姆问我是否看过这本书 。
* I want to know whether it's good news or not. 我想知道是否是好消息。