His writing is so confusing that it's difficult to make out ________ it is he is trying to express.(2011·安徽)
Experts insist that packets of cigarettes come with a health warning ______ to them.
— Tom, could you give me a hand in the following exam?— ______. Mom won’t allow me to do such crazy things.
Never before______ such a wonderful park, ______ I'd like to pay a visit again.
The manager asked me to______ the report, because he didn't want to speak for a long time at the meeting.
With the word "PM2.5"______ heard and seen in our life, people become more and more concerned about air pollution.