These diagrams are especially helpful when we have aconcrete problem ______ at hand

Once a year, people take part in “_______ Lights” activity to help save energy.

With a lot of difficult problems ________, the newly-elected president is having a hard time.

The vegetables grown in this district aremuch better than ____ in that district.

There is _____ with my bike. I must ask Uncle Wang for help.—Oh, sorry to hear that.