He does not know ______ they will plant trees on Saturday or not.
________ can help people be strong.
Kate wants to be slim. _____ she never eats fast food ____ sweet snacks.
Can you _____ the meaning (意思) of the sign (标志)?
—________ does your mother go to work?— She often goes there ______ the bus.
The pair of glasses over there ________ cool. Bring ________ to me and let me have a look.