The manatee（海牛）is a large marine mammal（海洋哺乳动物）. Manatees are also known as sea cows because of their slow, lazy nature and their grassy meals. Although they have such a name, they are more closely related to elephants. Manatees and elephants evolved from the same ancestor（祖先）over 50 million years ago.
There are three kinds of manatees. The West Indian manatee lives along the North American east coast from Florida to Brazil. The Amazonian manatee inhabits（栖居在）the Amazon River and the African Manatee swims along the west coast and rivers of Africa. Manatees differ in size from 2.4 to 4 metres and can weigh 200 and 590 kilograms. Though they may seem cumbersome, manatees can swim quickly and beautifully. Manatees usually swim about 8 km/h, but they can swim up to 24 km/h when they feel a need for speed.
Like whales and dolphins, manatees breathe air. They go to the surface for air every three to five minutes. However, they can hold their breath underwater for up to 20 minutes. This may have to do with the size of their lungs, as they are a large part of the manatee’s body.
Manatees have been under attack by humans for a long time, threatened by fishing nets and coastal development. The IUCN’s Red List of Threatened Species lists all manatees as vulnerable（脆弱的）or endangered and facing a high risk of dying out.
【小题1】Why are manatees also known as see cows?
| A．Both manatees and cows are mammals. |
| B．Manatees and cows have similar natures. |
| C．Manatees and cows have the same ancestor. |
| D．Manatees and cows appeared at the same time. |
【小题2】What can we know from paragraph 2?
| A．Manatees are sorted by where they live. |
| B．Manatees are too heavy to swim very fast. |
| C．Manatees’ swimming speed is over 24 km/h. |
| D．Manatees weigh differently in different places. |
【小题3】What does the underlined word “cumbersome” probably mean in paragraph 2?
| A．Large and lazy. | B．Large and strong. |
| C．Heavy but quick. | D．Ugly but strong. |
【小题4】What will the next paragraph of the passage probably talk about?
| A．Why manatees have been under attack by humans. |
| B．The introduction of other kinds of marine mammal. |
| C．How to protect manatees from dangers or extinction. |
| D．Some further information about the nature of manatees. |
【小题5】Which of the following is the best title for this passage?
| A．Elephants in the Sea | B．Three Kinds of Manatees |
| C．Protecting Sea Cows | D．Manatee, an Endangered Animal |
