题目

鉴别空气、氮气、氧气三瓶气体的最佳方法是(     ) A、测量三瓶气体的密度    B、用燃着木条分别伸入三瓶气体中 C、测量三瓶气体的溶解性    D、用带火星的木条分别伸入三瓶气体中 答案：BFinally, the long-awaited flying car is almost here. AeroMobil, a Slovakian company, plans to start selling its creation, the AeroMobil3. 0, in 2017. The company claims on its site that the vehicle “transforms in seconds from an automobile to an airplane" by using “existing infrastructure created for automobiles and planes."The vehicle is petrol-powered and has wings that fold, which allows it to be parked like a car, though it is nearly 20 feet long.The company's website features a video where the AeroMobil 3. 0 drives out of a hangar (飞 机棚 ）and goes down a highway, sharing the road with ordinary cars until it arrives at an airstrip. The car then unfolds its wings and takes off from a stretch of grass, rather than a paved tarmac (柏油路面), and flies through the air like any other small airplane.AeroMobil spokesman Stefan Vadocz said his company hasn't decided on an exact price because it's not ready yet."The prototype is a work in progress," he said in an email. But he said the price would be several hundreds of thousands of euros---somewhere in between a sports car and a light sports aircraft.The vehicle seats two people---the pilot and a passenger---and its single propeller (螺旋桨) is located at the rear of the plane. The company said the car's top speed on the road is at least 99 mph and while flying it is at least 124 mph. It can fly for 435 miles before running out of fuel. It has a steel framework and carbon coating and is powered by a Rotax 912, a four-cylinder (气缸) aircraft engine from BRP of Austria. Flying cars aren't exactly new. The concept has been around since long before The Jetsons popularized the idea in the 1960s. It has been a regular topic in Popular Science ever since World War I ace, Eddie Rickenbacker, wrote about it in 1924. But getting a practical, reliable flying car off the ground has been a serious challenge. Glenn Curtiss discovered this in 1918 when he developed the Curtiss Autoplane. It turned out to be more of a hopper than a flyer, so it failed to become popular with the public.1.What allows the AeroMobil3. 0 to be parked as a car? A. Its steel framework and folding wings.B. Its petrol-powered engine and folding wings.C. Its 99mph top speed and petrol-powered engine.D. Its ordinary car engine and folding wings.2.What is the biggest difference between the AeroMobil 3. 0 and other airplanes?A. It is powered by aircraft fuel. B. It can fly as fast as airplanes.C. It has a propeller.D. It can take off from a stretch of grass.3.What can be inferred from the passage?A. The AeroMobil3. 0's price will fall very soon.B. The design work on the AeroMobil 3. 0 is still in progress.C. The price of the AeroMobil 3. 0 will be higher than a light sports aircraft.D. The price of the AeroMobil 3. 0 will be the same as a sports car.4.What is the main purpose of the fifth paragraph?A. To describe some of the features of the AeroMobil3. 0.B. To explain why the AeroMobil3. 0 is better than an airplane.C. To explain the difference between the AeroMobil3. 0 and other airplanes.D. To explain why the price of the AeroMobil 3. 0 is high.