According to the passage, how many major networks are there?

• A、Two.
  
  

• B、Three.
  
  

• C、Four.
  
  

• D、Five.
  
  

下面的短文有5处空白，短文后有6个句子，其中5个取自短文，请根据短文内容将其分别放回原有位置，以恢复文章原貌。

Endangered Species Reading:Polar Bear Makes the List

In Spring 2008,the polar bear was placed on the endangered species list. According to the Endangered Species Act,an endangered species is an animal that is likely to face extinction in its natural habitat. __26__ The ESA defines a threatened species as one that is likely to become“endangered”in the foreseeable future.

The polar bear is the first animal that has been classified as endangered due primarily to global warming. __27__ Heating homes,driving cars,and burning garbage all require fossil fuels that lead to global warming.

The polar bear's habitat is more vulnerable to global warming than many other species. Polar bears live mainly on the sea ice in the Arctic. __28__ When the ice melts many polar bears move to land and live off their stored fat.In the Arctic, global warming is causing the ice to melt slightly earlier and form slightly later. This results in a shorter feeding season for the polar bear. Some risk their lives to find ice.If they have to swim too far they will drown from exhaustion and hunger.

__29__Every species of plant,animal,and insect there is threatened by global warming. Nevertheless,environmentalist groups such as the World Wildlife Fund often study large carnivores in order to assess the health of an ecosystem (生态系统) . __30__ In addition, donations are more commonly offered for the protection of large animals such as bears or elephants. People in general are less interested in conservation efforts that protect small wildlife, such as plants or insects. However,by using donor money to protect the habitat of the larger animals (ex.reforestation programs ) ,entire ecosystems can be protected.

It is important that animals such as the polar bear make it onto the endangered species list.

Once they are on the list there are laws that protect these animals from being hunted for food or sport. Agencies also receive money and tools to protect the habitat and recover the species. The goal of removing the animal from the list is often achievable.In fact,it is rare for a species to go extinct after they make the list. Sadly many species do go extinct while waiting for consideration.

 

A. But adding polar bears to the nation's list of endangered species,as some are now proposing, should not be part of those efforts.

B. Global warming is caused by carbon dioxide and other greenhouse gases that become trapped   in the atmosphere.

C. The Arctic food chain relies on the polar bear.

D. It is not only the polar bear that is at risk in the Arctic.

E. This is where they hunt for fish and build up fat reserves.

F. Polar bears have been categorized as a“threatened”species.

天津的一项调查发现，98%的高校生和92%的小学生都把周末用来做作业。请根据这个 调查说明你的看法，写一篇150词左右的英文短文。