下列各句中，没有错别字的一项是（      ）

根据各种无脊椎动物不同的形态特征，科学家将无脊椎动物分成了许多类。例如，海蜇、水螅属于  ____     动物；涡虫、血吸虫等属于 ____      动物；蛔虫、蛲虫等属于   ____    动物；蚯蚓等属于  ____     动物；蜗牛、螺、蚌、乌贼等属于 ____      动物；蚱蜢、虾、蜘蛛、蜈蚣等属于  ____     动物。

数学家欧拉在1765年提出定理：三角形的外心、重心、垂心依次位于同一直线上，且重心到外心的距离是重心到垂心距离的一半，这条直线被后人称之为三角形的欧拉线．已知△ABC的顶点A（2，0），B（0，4），且AC=BC，则△ABC的欧拉线的方程为（　　）

     The undersea world is very beautiful. Now more and more people want to dive in the water to find the secrets there. Scuba diving is a sport today. It can take you into a wonderful undersea

world.

      You will find many strange animals in the sea. Some are as large as a school bus. Many sea animals give out light in the dark and some have sharp teeth.

      During the day there is enough light. Here, under the sea, everything is blue and green. When fish swim nearby, you can catch them with your hands. When you have bottles of air on your back, you can stay in deep water for a long time. However you can't dive too deep. And you must be very careful when you dive in deep water.

      The deep sea is not an easy place to live in. It's cold, and it's dark, too. The deeper it is, the less sunlight there is. At about 3,000 feet, there is no light at all. It is very dark in the sea. Many fishes have no eyes. Some have big eyes. A few have eyes on one side.

      Besides the cold and the darkness, deep-sea animals face a third danger--other animals.

      Animals eat! They must find food to eat. Many animals eat plants. However, some animals eat meat. This means these sea animals have two jobs. They need to find animals as food, and they have to try not to become other animals' meal.