1931年的一个夜晚，沈阳北郊上空弯月高悬，突然一声巨响，南满铁路柳条湖的一段路轨被炸，打破了东北大地的宁静…此段描述反映的历史事件是（　　）

2016年3月3日科技报消息，科学家预言，地球上第六次生物大灭绝已经不可避免的开始了，而人类作为地球上的生物物种之一，虽然是当之无愧的统治者，但也难逃波及，而且，一旦生物大面积灭绝之后，人类很有可能随之灭亡，你认为导致第六次物种大灭绝的最主要的原因是（    ）

    My friend Tom is a schoolboy. Everyone likes him very much because he is kind. He likes to help people. He is a smart boy and he can play many musical instruments(乐器). After school, when he is with his friends, he often plays musical instruments for them. On weekends, he is free and he always goes to the old people's home. He plays the violin and the guitar to make them happy. He thinks it's interesting and fun.

    Today is February 28th. It's Tom's birthday. He has a big and interesting party at home. Many friends come to his party. Tom's mother cooks a lot of food for them. Everyone gives a beautiful gift to him. Sally gives him an English dictionary because Tom also likes English. Bob gives Tom a guitar because he likes playing the guitar very much. At the party, Tom plays the guitar and he also plays the piano. We sing many songs and play some interesting games. We have a good time today.