The window is never opened ____ in summer.
It was ______ Asimov was eleven years old ______ his talent for writing became obvious.
—Sorry, I made a mistake again. —______. Practice more and you’ll succeed.
I’d like to ______ you _______ your success on the experiment.
It is generally believed that teaching is ______ it is a science.
He raised his voice to make himself _______ clearly by the audience.