I wonder how he could __________ not handing in his maths exercises yesterday, for his maths teacher is always strict with his students.
In a time of social reform, people’s state of mind tends to keep _______ with the rapid changes of society.
Mr. Barren doesn’t think that all bad language should be allowed. In his opinion, there are ___________ that should be kept up.
—Correct ____ is important. —I agree. I don’t eat sweets now, for I’m on a _____.
Swimming is ___ in summer.