题目内容：

Air pollution is a leading cause of cancer and classified among top human carcinogens (致癌物质), said the International Agency for Research on Cancer (IARC), which is the World Health Organization's (WHO) cancer agency, on Oct 17,2013.“Our task was to evaluate the air everyone breathes rather than focus on specific air pollutants,” the IARC's Dana Loomis said in a statement. “The results from the reviewed studies point in the same direction the risk of developing lung cancer is significantly increased in people exposed to air pollution.”
    In 2010, lung cancer resulting from air pollution killed 223,000 people worldwide, and there was also convincing evidence that it increases the risk of bladder (膀胱) cancer. Loomis said people in Asia, Eastern North America, some places in Central America and Mexico, as well as North Africa have relatively high exposure(暴露). Developing countries with large populations and booming manufacturing sectors, such as China, are particularly at risk. This week, Harbin, the capital city of Heilongjiang province, became the first Chinese city to officially suspend classes due to serious smog, really good for teachers and students.
    Many developed countries face similar problems, although to a lesser（较少的、次要的） degree than most developing nations. Between 91 and 96 percent of Europeans living in cities are exposed to levels of PM2.5—tiny particles with a diameter of less than 2.5 micrometers—that are higher than the WHO safety limits.
    Although both the composition and levels of air pollution can vary dramatically from one location to the other, the IARC said its conclusions apply to all areas of the world. “Given the scale of the exposure affecting people worldwide, this report should send a strong signal to the international community to take action without further delay,” said Christopher Wild, director of the IARC.

1.What’s the main task of IARC?

A. To focus on cancer-causing substances.

B. To evaluate the air quality.

C. To study the developing risk of cancer.

D. To send signals to the international community.

2.The underlined word “suspend” in Paragraph 2 probably means ______.

A. accelerate  B. acknowledge  

C. delay   D. decline

3.Why should the international community take action without further delay?

A. A large number of people worldwide are exposed to air pollution.

B. More and more people in developing countries are exposed to air pollution.

C. Developed countries face air pollution, the level of which is higher than the safety limits.

D. The composition and levels of air pollution vary from place to place.

4.What might be the best title of the passage?

A. PM2.5，bad effect.

B. Safety limits of air pollution.

C. Signals of air pollution.

D. Air pollution, cancer risk.