题目内容：

    Jellyfish (水母) mainly live in oceans. Some can also live in fresh water. Unlike real fish, jellyfish do not have backbones. In 1., they don’t have any bones at all. They don’t have brains, eyes, ears and hearts, either. However, Jellyfish do 2. (good) without these body parts. Jellyfish live in every ocean in the world. There are hundreds of kinds of jellyfish. The number of jellyfish keeps 3. (increase).

Unlike real fish, jellyfish do not have fins or tails to help them swim. Instead, they open and close their bodies, getting water in and out. When they push water out, they move upward. Jellyfish can sense light and smell. They can find fish and plants to eat. They catch food with their tentacles(触手). Jellyfish can be dangerous because they sting (蛰). Some jellyfish stings hurt a little. Some hurt a lot. Some can kill. If you go swimming in a sea, 4. (be) careful of jellyfish. Get out of the water if you see them. If you see a jellyfish on the sand, don' t pick it up. If you get stung by a jellyfish, go to the nearest hospital quickly. There are many kinds of jellyfish. The smallest jellyfish are the peculiar creeping jellyfish, which are Just 0. 5mm to a few mm across. The5. (large) jellyfish are the lions mane jellyfish, whose body can be 2m across, with much longer tentacles.