30. Only those who have experienced hardship ____ well aware of what happiness means.

(2014·临川一中检测)Hurry up！The train________.You know it________at 8∶00 am

Bill, can I get you anything to drink— __________.

Take the advice ________ is given by Dr. White.

Why do you speak in _________ a loud voice—-Because I want to make myself ________ clearly.