She ____ to her hometown several times.
Having a walk after supper is certainly good for the old people, but it remains ______ whether they will enjoy it.
If better use is _______ your spare time, you will have a more brilliant future.
The fire made _____ difficult to rescue the people trapped under the ruins in the earthquake.
The world will be different, and we will have to be prepared to ________ the change.
You were silly __________ your car, otherwise it wouldn’t have been stolen.