题目内容：

Passage 2(2017届河南豫南九校高三下期质量考评)

体裁	话题	词数	难度	正确率
应用文	狗什么时候第一次成为＂人类最好的朋友＂和＂世界上最喜爱的宠物	334	★★★☆☆

Have you ever wondered when dogs first became ＂man’s best friend＂ and the world’s favourite pet? If you have then you’re not alone. When and where dogs first began living side-side with humans are questions that have stirred hot debate among scientists. There are a few hard facts that all agree on. These include that dogs were once wolves and they were the first animal to be domesticated(驯养) by humans. They came into lives some 15000 years ago, before the dawn of agriculture.

Beyond that, there is little agreement. The earliest bones found that are unquestionable dogs and not wolves date from 14,000 years ago. However, 30,000-year-old skulls have been discovered in France and Belgium that are not pure wolf and some scientists think could be dogs.

With such puzzling evidence, many scientists are now turning to DNA to find out when and where dogs were first domesticated. In one research project, tens of thousands of blood samples have been taken from street dogs around the world. The plan is to compare them with those of wolves. It’s even possible to analyse DNA from ancient bones. Tiny pieces of the 30,000-year-old skulls mentioned earlier are currently being studied, and another DNA study has already shown that ancient dogs preserved in the Alaskan ice-fields evolved from Asian wolves, not American ones.

Indeed, the ancient DNA may turn out to be more informative than the DNA of living dogs. Because dogs have accompanied humans around the world for thousands of years, their current distribution may tell us very little of their origins. This is why different groups of scientists believe that dogs variously originated in eastern Asia, Mongolia, Siberia, Europe or Africa.

But why were the animals domesticated in the first place? The most recent theory is that dogs domesticated themselves, initially living in and around our ancient villages to eat any food thrown out. Today, this is a way of life still shared by three -quarters of a billion unowned dogs worldwide.

1.Which is the only statement generally agreed on by scientists studying dogs?

A. They originally were used as farm animal

B. They evolved from wolves found in Europe

C. They helped the development of agriculture

D. They were the first animal to be kept as pets

2.Why does the writer first mention the 30,000-year-old animals skulls?

A. To show that dogs were much larger in the past

B. To prove that dogs developed from Asian wolves

C. To suggest that dogs may have evolved much earlier

D. To argue that dogs were first kept in France and Belgium

3.How did scientists determine the origins of the ancient dogs found in Alaska?

A. By examine the animals’ DNA

B. By analyzing the age of their bones

C. By studying the shape of their skulls

D. By comparing them with modern dogs

4.Why did dogs start living with humans?

A. Because they were attracted by food

B. Because they were trapped by humans

C. Because they couldn’t survive in the wild

D. Because they were trained to protect villages