Susan McWilliams, age 8, of Ashland, Ky., for her question:

DO ALL SHARKS ATTACK PEOPLE?

There are more than 250 different kinds of sharks in the oceans of the world, and only about 25 species are considered dangerous to human beings.

But most of the shark attacks that do occur result in serious injury or death. For this reason, swimmers should take special care in areas known to have dangerous sharks.

We once thought that sharks ate constantly and would therefore attack any human being immediately. But scientists now tell us that these fish can go for weeks or even months without feeding. During this time, the oil stored in their liver nourishes them.

Scientists do not know why some sharks attack people while most of the others leave them alone. There are fewer than 100 shark attacks a year reported throughout the world.