在进行主题为“中国人民志愿军一最可爱的人”的研究性学习时，可以作为史料运用的是（　　）

①当时的文献资料                    

②历史博物馆内存放的有关实物资料

③电影《上甘岭》

④当时的实况纪录片和照片

《中国知识分子论》中说：“‘圣君贤相’互相制衡的局面在历史上实在少见，也许只有史家绝称的‘贞观之治’勉强可以接近这种思想。”这种相互制衡的制度是(　　)

如图是机翼的模型，当飞机飞行时，迎面吹来的风被机翼分成两部分，机翼上方气流速度____ 下方气流速度，机翼上方的气压____ 下方的气压，因此在机翼的上下表面产生了____ ，飞机获得向上的____ ．

    Hi everyone! Good news. A book sale.____will people drive cars in space? Will you meet traffic ____? You'll get answers from our books. Are ____ interesting for you? They can do heavy work. You ____enjoy short working hours. We've got some storybooks about them. What's the best way to buy products at very good prices? Our books will tell you something about online ____? 

    Welcome to the playground this Saturday.

    Have a nice day!