Question

Living in the wild can be hard.Finding food and staying safe aren't easy.Each day,animals struggle to survive in their habitats.Not all animals get by on their own.Some animals form a close partnership with other kinds of animals. These pairings are called symbiotic (共生的) relationships.

In a symbiotic relationship,the animals depend on each other.One animal helps the other meet its needs.Sounds good,right?Not always.Some animals are not very kind to their partners.In some cases,one animal meets its needs but hurts its partner.Take ticks,for example.These insects suck blood to live.To get blood,they attach themselves to other kinds of animals.Ticks can pass germs that cause disease instead of helping their hosts.

In other relationships,animals don't treat their partners so poorly Both animals benefit from living with the other animal.

Small animals called cleaner shrimps have found a way of helping fish at coral reefs.As their name suggests,the shrimps clean the fish.They hang out at what scientists call a cleaning station.A fish stops by.Then a shrimp climbs onto the fish and even steps into the fish's mouth.The shrimp uses its tiny claws to pick stuff off the fish's body.That can include dead skin,tiny pieces of food,and wee creatures that can hurt the fish.The fish gets a nice cleaning.The shrimp enjoys a tasty meal offish trash.

Small birds called plovers are also in the cleaning business.They have big customers—crocodiles.Crocs have long snouts（鼻子）filled with sharp teeth,Cleaning them is tricky.When a croc opens its mouth,the plover hops right in.The croc does not snap its snout shut.Instead,it lets the plover eat small,harmful animals attached to its teeth.The plover gets an easy meal while the croc gets clean teeth.

1.The text is mainly about     .

A. the hard life in the wild

B. animals in a symbiotic relationship

C. animals living together

D. some dangerous animals

2.According to the text,in a symbiotic relationship,      .

A. animals depend on each other

B. birds depend on animals for food

C. both sides can get help

D. not all animals treat their partners well

3.Why do the cleaner shrimps clean the fish?

A. To get fish trash for food.

B. To eat wee creatures.

C. To help fish go out of coral reefs.

D. To get food for fish.

4.According to the text,it can be inferred that     .

A. living in the wild can be hard

B. different animals have different living ways

C. crocodiles mainly live on plovers

D. ticks are useful to some animals

Answer

1.B

2.D

3.A

4.B

【解析】试题分析：本文主要介绍了生物界存在的共生现象。在自然界中，有些生物之间存在一种合作关系，它们相互依存，各取所需。

1.主旨大意题。纵观全文可知，本文主要介绍了生物界的共生现象。很多生物之间存在相互依存、相互帮助的关系。故选B。

2.细节理解题。根据第二段后半部分Not always.Some animals are not very kind to their partners.In some cases,one animal meets its needs but hurts its partner.Take ticks,for example.These insects suck blood to live.To get blood,they attach themselves to other kinds of animals.Ticks can pass germs that cause disease instead of helping their hosts.可知，并不是所有的动物都对它们的共生伙伴很友好，壁虱就是个这样的例子。故选D。

3.细节理解题。根据第三段最后两句That can include dead skin, tiny pieces of food, and wee creatures that can hurt the fish. The fish gets a nice cleaning. The shrimp enjoys a tasty meal offish trash.可知，清洁虾为鱼做清洁是为了得到鱼身上的垃圾做食物。故选A。

4.推理判断题。通读全文可知，动物们为了生存形成共生关系，但是他们并不是都能够友好相处，例如：壁虱吸食同伴的血液生存；清洁虾为鱼做清洁，并以清洁下来的垃圾为食；珩科鸟与鳄鱼友好相处。因此推断在大自然中，不同的动物有不同的生活方式。故选B。