题目

菜农为了增加大棚内蔬菜的产量，向大棚内施加气肥，气肥的主要成分应该是（ ）A．氮气B．二氧化碳C．氧气D．甲烷 答案：B解析:略We can't have lunch at the restaurant, because __________.A．not all of us have moneyB．all of us don't have moneyC．everyone of us don't have moneyD．none of us has money