What does PM 2.5 mean—It’s a professional ________ indicating the condition of air pollution.

His letter was so confusing that I couldhardly make any ______ of it.

are you doing this Saturday— I’m not sure, but I go to theRolling Stones concert

Could you tell me ______— By searching the Internet.

You _________ pay too much attention to your reading skill, as it is so important.