—You have no idea how to solve this math problem.—You should try to think about which principle can _______ it.
【原创】 Vehicles, coal-burning, airborne dust and industrial production ______85 to 90 percent of the major airborne pollution sources in most Chinese cities, the newest research shows.
【原创】 Green roofs have an ______effect, helping reduce the amount of energy______ to heat a building in winter and cool it in summer.
【原创】The hardest thing is to ______ less when you can ______more.
We need some more facts and figures we take the final decision.
Only you step into society can you learn practical things.