The World Health Organization has given some advice on        to protect us from being infected(感染） with H7N9.

My mother likes volleyball. She thinks (认为) it is _______.

---How delicious the coffee is!---That’s right. It will taste ______ with milk.

David watches TV six hours a day and eats much junk food, but he never exercises. So he is ___. 

The Internet is really            to us. We can download a lot of things from it.