Two years ago, three scientists traveled to the Antarctica to explore a secret world hidden _________ the ice.
54. --- I have two suggestions: one is to go to the cinema, the other is to have a drink. --- Well, personally I prefer the _____ one. I don’t like films very much.
53. In 1989, a(n) _______law was passed by the United Nations to stop people putting waste into sea.
52. The two American came to China for a visit. They visited many places ______ and enjoyed themselves.
51. In the low latitude area, it is usually very _____ all the year around.
50. Teachers should be _____ with their students but should not be _____ on them.