题目

下列化学方程式书写正确的是 A． CH2=CH2 + Br2 CH3CHBr2       B． C． D． 答案：B Each of us shares this planet with seven billion others． People and products need to move from city to city and country to country． However， most cars， motorcycles， boats and planes cause air pollution1.This is a serious problem． So inventors are coming up with creative ideas to reduce the pollution and noise．Motorcycles are a faster and cheaper way to get around a city than cars．2.To solve this problem， a company designed an environmentally friendly motorcycle． It uses electricity so there is no pollution．3.There are no cars in the city center． Instead of cars， water taxis and buses carry people around the city． However， they cause pollution． English engineers Dick and Jem designed a solar﹣powered water taxi．Planes also cause air and noise pollution．4.Some airplane companies have started to solve the problems． Swiss engineers have gone one step further．5. This plane holds the world record for the longest solar﹣powered flight﹣1，541 kilometers．A． They developed a solar airplane．B． Designing an environmentally friendly airplane is a real challenge．C． Yet air pollution is a growing problem．D． They are also noisy．E． The Italian city of Venice is a city with only a few roads．A． They developed a solar airplane．B． Designing an environmentally friendly airplane is a real challenge．C． Yet air pollution is a growing problem．D． They are also noisy．E． The Italian city of Venice is a city with only a few roads．