下列各句中均有一处错误，请找出来并改正。
( )1. My mother isn't at home and she has been to the post office.
( )2. Listen!The noise is becoming loud and loud.
( )3. I didn't go to school because my illness.
( )4. They are swimming at this time yesterday.
( )5. You should read as much books as possible in your free time.
( )6. It's still one of the most beautiful sight in the world.