It suddenly _____ him that he had taken the wrong bus.
You’d sound a lot more polite if you make a request ______ a question.
The questionnaire takes ______ ten to fifteen minutes to complete and can be used along with the assessment interview.
As there is less and less coal and oil, scientists are exploring new ways of making use of ______ energy, such as sunlight, wind and water for power and fuel.
In our class, when the bell rang and the teacher closed his book, it was a ______ for everyone to stand up.
Hiking by oneself can be fun and good for health. It may also be good for ______ building.