Although modem organic food has become very popular, many people can' t figure out the difference between organic foods and ______ grown foods．

Failure hurts adults and children ______ , but it can make a positive contribution to your life once you learn to use it.

This writer’s book sells ___.

---You are devoted herself_____ to her research and it earned her a good reputation in her field.

 He began to take political science_____ only when he left school.