题目

在中，若，则的角度为（    ） A．80°                        B．90°                        C．100°                      D．120° 答案：C 【解析】 根据平行四边形的邻角互补即可得出∠B的度数． 【详解】 ∵在▱ABCD中，∠A=80°， ∴∠B=180°-∠A=180°-80°=100°． 故选：C． 【点睛】 本题考查了平行四边形的性质，解答本题的关键是掌握平行四边形的对角相等，邻角互补的性质．We often think of future.We often wonder what the world would be like in a hundred years' time.Think of space, perhaps a permanent(永久的) station on the moon will have been set up.Perhaps people will be able to visit the moon as tourists.Cheap rockets for space travel will have been developed, permitting long journeys throughout the solar system(太阳系).When that time comes, people will be taking holidays in space and visiting other planets.Great progress will have been discovered for the most terrible of all diseases—cancer.Pollution is a problem we must solve.In a hundred years' time it will have been controlled.All the world will have been developed—even Antarctica.There will be large cities in Antarctica.We already have supersonic(超音速的) flight, but in a hundred years' time we will have supersonic land travel as well.We will have used up most of earth's land to build our cities, so floating cities will have been built.The Japanese already have plans for cities of this kind.And there will be cities under the sea.The first of these will have been completed.1.We will have developed __________ in a hundred years' time, permitting long journeys all over the solar system.A.cheap rockets for space travelB.a plane for space travelC.a permanent spaceshipD.a satellite for tourists2.Man will also have supersonic land travel ____________.A.in a year's timeB.about half a century laterC.in the year 2050D.about a century later3.The last paragraph mainly talks about _____________.A.new ways of building citiesB.the building of cities under the seaC.the building of floating cities in JapanD.the danger which earth's land will face4.The best title for the passage is ______________.A.Travel in the FutureB.Future LifeC.Where to Live in the FutureD.Space Travel