A、They should cut more trees and not use any materials harmful for human health. B、They should exploit fast-growing trees and re

Recent films, books, magazines and newspapers have reported about serious threats to the environment. Changes in climate, increasing pollution, rising energy demands, and decreasing supplies of water are worldwide problems. Designers and builders around the world are reacting to these environmental concerns with new conception of green house.
    Green houses are designed to be sustainable. Something that is sustainable provides people today with what they need. But it does not use up or damage the natural resources.
    Green houses use much less fossil fuels—oil, gas and coal—for energy. The houses are placed on the land so the sun warms them during cold months and is blocked during hot months. The houses have plenty of windows that open to let in cooling air. They have special equipment that uses a lot less water.
    Green houses are made of wood from fast-growing trees so old growth forests do not have to be cut. They include recycled materials so something old is re-used, not thrown away as waste. The houses are healthier for people to live in. Materials used in them are not processed with strong chemicals that can produce harmful gases.
    Houses that are environmentally friendly are not new. For years, architects in many areas of the world have designed and built them for environmental activists. But now, rapidly rising energy costs are increasing the demand worldwide for green houses that use less energy and other resources.