题目

设奇函数f(x)在[－1,1]上是单调函数，且f(－1)＝－1，若函数对所有的x∈[－1,1]都成立，当a∈[－1,1]时，则t的取值范围是______________． 答案： 根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有多余选项。 1.The goal here is to limit carbon dioxide and other greenhouse gases, which are closely associated to the big problem of global-warming. Strategy 1: Bring your own cup to Starbucks You’ll get a 10 cent discount, and it’s one less paper cup to end up in a landfill. While you’re there, pick up some free bags of spent coffee grounds to use as ‘‘green’’ fertilizer in your garden. The payoff:    2. Strategy2: Turn off your computer When in standby mode, your PC is still using energy.    3. The payoff: Turning off a monitor for 40 hours a week may only save $ 5 a month, but it reduces CO2 by 750 pounds Strategy 3: Reuse plastic bags Instead of throwing away 100 billion plastic bags a year, try and get a second, third, or tenth use out of them. Better yet, next time you shop, try a reusable bag. The payoff:     4.The amount of oil it would take to make just 14 plastic bags would run your car for one mile. Strategy4: Use recycled paper in the bathroom Most of the toilet paper we use is made from trees found in forests previously untouched by humans. The payoff: If every household replaced one roll of toilet paper with a recycled one, 424000 trees would still be standing. Look for eco paper towels too. Strategy5: Buy energy-efficient appliances（电器） Replace the old fridge with an Energy Star appliance and you’ll use 15 percent less energy.     5. The payoff: If we all used one Energy Star appliance at home, it would be like planting 1. 7 million acres of new trees. A. You can be proud of yourselves, even if you can only make one or two of these green changes. B. Adding green to your garden is beautiful and earth-pleasing. C. It might be a little expensive to buy, but you’ll save money on your electricity bills and help the environment. D. In fact, 75 percent of electricity used in your home comes from electronics that are turned off. E. You’re reducing pollution. F. The store won’t create more waste when they throw away a cup. G. Just one tree will help make cleaner air and save the environment from 5000 pounds of hot carbon dioxide each year.