81. Male and female students are quite different from each other ______ the age at which they begin to develop an intellectual self-discipline.
I hope you should achieve a ______ between your school work and your hobbies.
The coal miners ______ in the coal mine for 10 hours before we came to their rescue.
______ ,customers spend about 1.5 million pounds a day.
His father came out of prison ______ Dickens have a chance to go to school.
School children must be taught how to deal with dangerous ______ .