题目

松树和桃树相比，最主要的不同之处是（ ） A．松树的果实内有种子 B．松树没有果实，种子裸露在外面 C．松树的球果包裹着果实 D．松树的胚珠外面有子房壁包被着 答案：BWith the plane 　　　　in ten minutes, all the passengers on board were asked to turn off their mobile phones.A. taken off B. taking offC. to take off D. would take off