1 . Vitamin B could help lessen the effects of the most dangerous type of air pollution，according to a new study published recently. In the first study of its kind，a team of international researchers looked at the damage caused by one of the pollutants that has the most severe impact on health: PM2.5.

Particulate matter，or PM，is a type of air pollutant consisting of small particles of different sizes. PM2.5 has a diameter of fewer than 2.5 micrometers，about 30 times smaller than a human hair. These particles are so small that they can go into our respiratory system (呼吸系统), resulting in lung and systemic inflammation (炎症) and stress.

The team found that something as simple as a daily vitamin B supplement could potentially reduce the impact of the tiny particles on the human body，although they stressed that the research was in its early stages and the sample size was small.

For this study，10 volunteers were initially exposed to clean air and given a placebo (安慰剂) to check their responses. The group then took another placebo for four weeks before being exposed to heavily polluted air from downtown Toronto，where an estimated 1，000 cars pass every hour. The bad air was delivered to the volunteers through an “oxygen－type” face mask. The experiment was then repeated，with each volunteer taking a vitamin B supplement daily made up of 2.5 mg of folic acid，50 mg of vitamin B6，and 1 mg of vitamin B12. B6 can be found in liver，chicken and nuts，and B12 in fish，meat，eggs，milk and some cereals.

The researchers found that four weeks of vitamin B supplements reduced the damage of PM2.5 exposure by 28%－76%. The results highlight how prevention at an individual level could be used to fight the harmful effects of PM2.5.

1. Why is PM2.5 harmful to our health?

A．It pollutes and poisons the air.	B．It is too much to be got rid of.
C．It carries viruses and diseases.	D．It is easily breathed in and damages our body.

2. What can we infer from Paragraph 3?

A．The process of the research was not scientific.

B．This kind of research has been done many times.

C．Further studies are needed to confirm their findings.

D．Vitamin B is hard to obtain in people’s daily life.

3. What is the text mainly about?

A．International researchers have a new finding.

B．Vitamin B could reduce the damage of PM2.5.

C．Particulate matter does great harm to our health.

D．Emission control and regulation are badly needed.

4. The new study was probably published ________.

A．in a science journal	B．on a government website
C．in a fashion magazine	D．in a medical textbook