The traditional view is ________ we sleep because our brain is “programmed” to make us do so.
The climbers succeeded in climbing to the top of the mountains, and they owed their success to the preparations they ______.
The students expected there ____more reviewing classes before the final exams.
Such things ___ you described in the report seldom happen now.
At present, how we can look after ______ old is becoming ______ hot and severe issue.
It is the duty of the police to ______ social order.