A big dust storm covered Sydney for hours, ______ the Sydney Opera House invisible.
A great many students have dropped out of school and now the number of our class has____51.
The person____drugs had much difficulty in getting rid of the_____.
Years later, I began ______ what he told me right.
It’s no use ______ with him ______ this matter.
______ the distance was too long and the time was short, we decided to fly there instead.