词汇运用，用所给词的适当形式填空（共15小题；每小题1分，满分15分）
He said light _________________ faster than sound. (travel)
——What are you listening to? 
——Some new songs _________________ by Jay Zhou. (write)
The bike must be the _____________. He put it here before entering the Police Station. (witness)
My English teacher’s advice is of great _________________ to us students. (value)
_________________ this, humans on Mars will have to wear special boots. (prevent)
Hamlet is one of Shakespeare’s most famous tragedies(悲剧) written in his _________________ (forty).
Our planet is becoming_____________ than before. (crowd)
He has devoted most of his time to  _________________ the children. (educate)
I met Mary in the park yesterday. We _________________ each other for half a year since we left school. (not see)
The football match between Chinese Team and Korean Team _____________ live on CCTV-5 at 9:00 next Sunday. (cover)
He took off his boots and  _________________ them under the check-out. (hide)
We must try our best to stop pollution to live even  _________________.(comfortable)
Britain is the first country in the world _________a free health system. (have)
She likes talking to others while _________________ for the bus. (wait)
How many _________________ are there in this building? (enter)