人体及时发现与杀死癌变细胞的功能是（）

A.免疫防御

B.免疫耐受

C.免疫监视

D.免疫自稳

E.免疫清除

The word "sport" first meant something that people did in their (36) time. Later it often meant (37) wild animals and birds. About a hundred years ago the word was first used for (38) games, which is its usual (39) today. People spend their spare time playing football, basketball, tennis and many other sports. Such people play because they want to. Some people are (40) for the sport they play. These people are called (41) sportsmen. They may be sportsmen for only a few years, but many of them can earn a lot of money. Of course, it is only (42) for a few sportsmen to earn much money in sports for (43) , like golf, tennis and (44) racing. (45) . They allow the companies to use their names or photographs and are paid for this. (46)