When you have difficulty, do remember to _________. Two heads are better than one.

The fire lasted half an hour before it was ______ by the firemen.

Bill can play______ violin but he can’t play ______ basketball.

We are supposed ______ the lost child at once.

? Do you know the most ancient city in China ─ Xi’an well? ? No, this is the first time I ___________ here.