题目

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 pollution【1】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 o墨西哥湾泄漏的原油目前已基本清理干净。在清理过程中，科学家们发现了几种奇的能“吃油”的细菌，根据所学知识推测这些细菌没有的结构是A．细胞壁B．细胞膜C．细胞质D．成形的细胞核