【由江苏省盐城市2014模拟改编】
阅读理解。阅读下面短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。
Air pollution is a leading cause of cancer and classified among Group 1,or 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.
