题目内容：

Dogs are known for their sense of smell. They can find missing people and things. Now a study shows that the animal can even find bladder cancer (膀胱癌).

Cancer cells can produce chemicals with unusual smells. Scientists think dogs have the ability to smell these smells, even in very small amounts, in urine (尿).

For example, a dog showed great interest in the growth of its owner’s legs. The man was later found to have skin cancer. Carolyn Willis and some scientists trained different kinds of dogs for the experiment. The study used urine collected from bladder cancer patients (病人), from people with other diseases and from healthy people. Each dog was tested 8 times. In each test there were 7 examples for the dog to smell. The dog should show the one from a bladder cancer patient by lying down next to it.

Their results later appeared on the British Medical Journal. In all, 36 bladder cancer patients and 108 other people attended. During the training, all the dogs even found cancer in a person who had been tested healthy before the study. Carolyn Willis said dogs could help scientists find the chemicals produced by bladder cancer. The information could then be used to develop machines to test for the chemicals. The team also plans to use dogs to help find other kinds of cancer.

1.How many kinds of urine were collected in the experiment?

A. One.    B. Two.    C. Three.    D. Four.

2.Why did the writer give the detailed experiment in the third paragraph?

A. To introduce the first paragraph.

B. To support the second paragraph.

C. To teach us to do some experiments.

D. To let us know the reason of the experiment.

3.What would the dog do when it found the right urine?

A. It would lie down next to its owner’s feet.

B. It would take the urine to the scientists.

C. It would lie down next to the urine.

D. It would make some noises.

4.What’s the main idea of the passage?

A. Dogs have a good sense of smell.

B. Dogs can help people become healthy.

C. Dogs can be used in experiments.

D. Dogs can smell cancer.

5.Who may be most interested in reading the passage?

A. Dog owners.    B. Doctors.

C. Pet lovers.    D. Singers.