—Jim, is physics difficult to learn in high school? —Sure. No subject can be learned well ________ hard work.
Her mother didn’t allow her _________ computer games at all.
Take more exercise every day, or you may ___________.
—______ can you cure my father, Doctor? — In about a week.
Smoking is bad ___________ health. You must give __________.
Since then, my aunt many homeless children.