After _______ absence of 10 years from his hometown, Mr. Li doesn't know _______ great changes have taken place there.
All the scientific evidence ______ that increasing use of chemicals in farming______damaging our health.
It is required that the students _____ mobile phones in their school, so seldom _____them using one.
Nuclear ______ be really dangerous at times even though it’s a nice energy in general.
When reading English novels, I often idiomatic expressions that I can't understand.
Hardly _ when they realized that it was too late to catch the last train.