A good teacher should leave some time for the students to __________ the knowledge.

Aren’t we living a happy life–You should not be content with what you have._______, you must be better in every aspect of your life.

Again and again the doctor _____ the crying girl, but he couldn’t find out what was wrong with her.

______ am a girl. _______ name is Wang Lei.

This also keeps the air，soil，water crops________ chemicals