There is _____pollution and ____fishes in the river now than 20 years ago.
It’s good _____ old people to cross the road.
—Lily, here are your pens. Please _____ . —OK, Mom.
— _____ do you _____ English? —I like it very much.
—How many _____ are there in your class? —About 63.
The sign means “ _____.”