Trees are useful to man mainly in three ways, the most important of which is that they can protect ______ from droughts (干旱) and floods.
To keep the town clean, the truck ____ garbage is prevented ____ entering the town.
I rely ____ her to pay back the money.
Waste paper, waste glass, and waste iron can all be _____.
Food supplies may ________ towards the end of the trip, so we can’t waste any food.
Be ____ to finish your homework before supper.