I have to buy _________of the two books because I don’t know which to choose.
—Excuse me, can you give me a _______? —Sure.
—_______ I borrow your English book? —Yes, of course you _______.
Do you prefer _______?
—Mr. Hu, can you tell us how to learn swimming well? —Sure. But remember we can learn nothing well _______ hard work.
You _______ wash your hands before meals. It is good for your health.