—Clean-Up Day is coming. How do we let more people know it?—We could ____ advertisements after school.
Scientists are trying their best to_______ ways to treat the terrible disease caused by Ebola(埃博拉).
—What shall we do this Saturday? —it rains, we’ll have a picnic in Century Park.
It's a pity that I didn't think of ringing you.
To remember things accurately, we don't allow other thoughtsour mind.
If you travel around the world, you will be surprised at ________.