He is so busy. He cannot afford enough time with his son ____he wants to.
. _______ different kinds of pianos, the workers farther improved their quality.
A person _______ a foreign language must be able to use the foreign language _______ all about his own.
.The wallet _______ several days ago was found _______ in the dustbin outside the building.
.Lessons _______ easily were soon forgotten.
The ground is _______ with _______ leaves.