题目

化学与生产、生活密切相关，请按要求填空：空气中体积分数约为78％的气体单质是                  ；可作复合肥料的一种盐是           ；沼气（主要成分CH4）完全燃烧的化学方程式是                                           ； 答案：氮气（N2）         硝酸钾（KNO3）等             The manager had something more important to do, as a result he couldn’t _________ here this evening． [　　] A．pick up B．take up C．make up D．turn up