完形填空

Sharks have been on earth for 　　1　　 of years．There are between 200 and 250 kinds of sharks．They come in different 　　2　　．The largest can be as long as 15 metres．It eats plants from the sea, but many sharks feed 　　3　　 fish, other sea animals, smaller sharks and 　　4　　 they eat people．It is said that one of the most 　　5　　 sharks in the great White Shark．They have attacked(袭击)a number of people off the 　　6　　 of America．Australia, New Zealand and South Africa also have shark attacks．In some places there are watchtowers on the beaches to warn people about sharks in the water．When a shark 　　7　　, a bell rings to 　　8　　 the people to get out of the water．Sharks 　　9　　 about 100 people a year in the world．Perhaps the shark just thinks that the person is a kind of 　　10　　 animal, or something good to eat．