题目

Where do you go when you want to learn something? School? A friend? A tutor? These are all _______places of learning. But it may well be that the learning you really want _______ somewhere else instead. I had the chance of seeing this first hand on a _______.My daughter plays on a recreational (业余) soccer team. They did well this season and so _______ a tournament, which normally was only for more skilled club teams. This led to some _______ experiences on Saturday as they played against teams _______ trained. Through the first two games, her team did not get one serious shot on goal. As a下列物质必须隔绝空气保存的是①Na   ②Na2O  ③Na2O2  ④NaOH    ⑤Na2SO4A．①②③④⑤B．①②③④C．①③D．①③④