People have planted a great many trees in order to ________ wind and sand in the desert.
down the radio a little—the baby is sleeping.
—Who’s knocking at the door? —Maybe wanting to sell some new products.
The house could fall down soon if no one some quick repair work.
My cell-phone has disappeared. Who have taken it away?
We can imagine city of Wuhan in year 2030 will be different from what it is now.