When the expression first came into being, people refused to use it but _____ they began to accept it.

He tries _____English well. And he practices _____English every day.

He is so careless that he often ______ his school things at home.

“How many students have visited The Summer Palace” “.”

The father seldom had time to share with his children, because he devoted most of his time _______ research in his lab.