No one knows ____ .
Good hobbies can help us _________and make our Iives _________
----Do you know_____ second-hand smoke? ----To prevent our health and memory.
---- Will you buy this tie for Dad? ---- I have no idea. I don’t know or not the colour matches his new shirt.
The child is too young to_________ himself.
You can never imagine what great difficulty I have _________ your house.