题目内容：

    Joshua Plotnik and his colleagues carried out the tests on six 12-45-year-old Asian elephants living in the grounds of a hotel in northern Thailand. The buckets containing the seeds were not clear enough to see through and had a lid with small holes to let the smell out. In experiments, the elephants chose the greater quantity of seeds in each pair, regardless of the quantity of seeds presented. The accuracy of the prediction was better when the difference between each pair increased.

This is thought to be the first time that an animal is able to use its sense of smell to make a simple calculation of whether one of two quantities is more or less than another-the most basic form of math.

Many animal species have shown an ability to tell apart between more and less when presented with different amounts of food. But they have used vision to discriminate. Dogs have been unable to show they can perform the same trick in tests of their abilities to smell.

For an elephant this ability could be very important. Elephants often travel long distances to find better-quality food and water, which can differ according to seasonal availability, changes to their environment, and a risk they could be attacked by humans. The best performers were able to get it right more than 80 per cent of the time.

The scientists suggest that male elephants are better at the task because they need to eat more food, making it more important that their sense of smell is keener. Males also have to sniff out females in heat over long distances in order to reproduce.

They say that while elephants do use vision, particularly in close contexts where they react to each other’s body language, they use it mainly to match their more powerful senses-hearing, smell and touch.

That elephants have a powerful sense of smell is perhaps unsurprising. They have more genes related to smell than any other animal: 2,000 compared to around 800 for a dog.

1.What special ability do elephants have?

A.Use their trunks to find different smells.

B.Distinguish between more and less food.

C.Smell the differences of food quality.

D.Per form the basic math calculation.

2.What does the underlined word “discriminate” mean?

A.Choose. B.Indicate.

C.Measure. D.Distinguish.

3.Why do elephants often travel long distances?

A.To find where the better food is.

B.To find where humans wait to attack them.

C.To find where the environment has changed.

D.To find where they can adapt to the climate.

4.What is the best title for the text?

A.Elephants can do simple math puzzles

B.Elephants can “count” with their trunks

C.Elephants can smell the quality of food

D.Elephants can use vision to communicate