题目内容：

Pigs are always considered dirty animals because they roll in mud．But in fact they prefer  being quite clean．They cover themselves with mud to help stay cool．During cooler weather,  they prefer to stay clean．So do elephants, who also cover themselves in dust or mud to keep cool．When they find a place with clean water they will take a bath，using their long noses to give  themselves—or each other—a nice shower

Some animals use dust to get clean．Chinchillas (南美洲栗鼠) have very fine fur． They don’t like to take water baths because water is not warm enough for them．So, instead, they roll  around in fine dust．The dust helps to keep their fur and skin dry．This protects them from disease

Usually, a small bird is a light meal for a crocodile．But when a crocodile wants its teeth  cleaned．it lies on the ground with its mouth open．The crocodile bird goes in and picks out any  parasites(寄生虫)between the crocodile’s teeth or under its tongue．The crocodile gets its mouth cleaned，and the crocodile bird gets dinner．

You wouldn’t think fish would need baths．But some undersea parasites live under the  fish’s skin．“Cleaner” fish，like the wrasse(隆头鱼)，help take them away．The wrasse stands on its head and dances to signal a big fish that it is ready to go into the cleaning business．The big fish will stop moving and open its mouth wide so the wrasse can swim inside and pick out  parasites and bits of food．

1.The passage is mainly about how animals __________．

A．stay clean    B．help each other    C．get their food D．take baths

2.What can we learn from the first paragraph about pigs?

A．They can help each other take baths．     

B．They are dirtier during cooler weather．   

C．They prefer taking baths to rolling in mud．

D．They like to stay cool and clean．

3.Chinchillas use dust to get clean for the following reasons EXCEPT that ________．

A. dust can dry their fur and skin         B．They are not good at swimming

C．Water is too cold for them           D．Dust is good for their health

4.From Paragraphs 3 and 4，we can know that __________．

A．Some animals can get clean from others’ help

B．Most animals are friendly to each other

C．Small animals couldn’t get food from big ones 

D．All of the animals prefer to stay clean