What is the main idea of the news item？A．Some of the office workers have breathlessness.B．

What is the main idea of the news item？

A．Some of the office workers have breathlessness.

B．Few milk powder factory workers experience wheezing.

C．Mothers and babies benefit the most from respiratory tests.

D．There is a link between asthma and exposure to milk powder.

请帮忙给出正确答案和分析，谢谢！