Hiking by oneself can be fun and good for health.It may also be good for ________ building.
—Did you have a good time in Veitnam last week?---______, it was too hot.
—Beijing experienced _____ heaviest snowfall in ____ month of January .
We already have ______pencils, but we need two ____ pens.
Why are you leaving right now? You promised to stay ____ hours.
We asked John and Jerry, but ____ of them could offer a satisfactory explanation.