Public service advertisements are often run free, and are to educate people about health, safety, or any other issue which affects public welfare.
A. for, mean
B. for, meant
C. of, to mean
D. in, meaning
网友回答
A. for, mean
(答案→)B. for, meant
C. of, to mean
D. in, meaning
解析：考查固定搭配。 fot free免费;be meant to do旨在做某事。公共广告是免费经营的而且旨在教育人们关注影响公共福利的事情像健康、安全以及其他问题。