题目内容：

A healthy amount of sunshine may be the secret to staying young. British scientists have discovered.

Vitamin D is produced naturally by the skin in response to (对…的反应) sunlight and may help to slow the ageing process and protect against heart disease, according to the study.

Researchers from King's College London studied 2,160 women aged between 18 and 79, looking at their telomeres-a biological marker of ageing found in DNA. As people get older, their telomeres get shorter and they become more susceptible (易受伤害的) to certain illnesses.

But the study found women with high levels of vitamin D had comparatively longer telomeres-a sign of being biologically younger and healthier.

The study suggests vitamin D may help to slow down the ageing process of DNA, and therefore the ageing process as a whole.

Lead researcher Dr Brent Richards said, "These results are exciting because they show for the first time that people who have higher levels of vitamin D may age more slowly than people with lower levels of vitamin D." This could help to explain how vitamin D has a protective effect on many ageing related diseases, such as heart disease and cancer."

Professor Tim Spector, a co-author of the report, added, " Although it might sound absurd(荒唐的), it's possible that the same sunshine which may increase our risk of skin cancer may also have a healthy effect on the general ageing process.

Vitamin D made by the action of sunlight on the skin accounts for 90 percent of the body's supply, but lower levels can also be got through food such as fish, eggs and breakfast cereals(粥).

Other studies have suggested the vitamin plays a key role in protecting against cancer and heart disease.

1.A certain amount of sunshine helps people stay young because _________.

A. people feel happy and energetic in the sun

B. vitamin D may help to slow the ageing process

C. sunshine protects people against heart disease

D. vitamin D makes one's skin look young and healthy

2.From Brent Richards, we know that ________.

A. sunlight causes skin cancer to people with high level of vitamin D

B. the study generally has a healthy effect on the general ageing process

C. the higher levels of vitamin D people have, the more slowly people may age

D. vitamin D can only be got from fish, eggs and breakfast cereals

3.What can we infer from the passage?

A. Sunlight does more good than harm to our health.

B. Telomeres are important as they are signs of ageing of the DNA.

C. Sunlight can be dangerous as it causes skin cancer.

D. Vitamin D can also be gained from food.

4.What is the best title of the passage?

A. Secret of Staying Young

B. Sunlight and Vitamin D

C. Vitamin D Helps Slow Ageing

D. Sunlight and Health