What do you read when you travelling by train? What about other passengers? Perhaps a woman____(sit) near you is reading a romantic novel. A man is reading a serious biography about a politician. And there's a student reading an English textbook.

    What do their____(choice) say about them? Do you judge them by____they reading? I have to tell you that your impressions of them may be____(complete) wrong. The woman reading the romantic novel could be a ____(law). She just wants a light read to take her mind off work. The man reading the biography wants you____(consider) him knowledgeable, and he is just ____(show)off. The student reading the textbook isn't a student at all. She's an English teacher.

    Publishers know people are ____ (concern)about what they read on public transport and put out different versions (版本) of a cover For example, books about Harry Potter have an____ (interest)cover for young readers and then another more serious version for adults.

    So next time you see what other people are reading on a train don't jump to any conclusions.

    Here is a situation ____ you could say, "Don't judge a book by its cover.”

如图所示的装置中,三个相同的弹簧在未受力状态下的原长相等，小球的质量均相同，弹簧和细线的质量均不计，一切摩擦忽略不计。平衡时各弹簧的长度分别为L₁、L₂、L₃，其大小关系是（     ）

已知命题p：x＞0，y＞0，q：xy＞0，则命题p是命题q的（　　）条件．

改革开放以来，中国有7亿多人口摆脱贫困，13亿多人民的生活质量大幅度提升，用几十年时间完成了其他国家几百年走过的发展历程。这说明改革开放是（  ）

如图，AB是半圆O的直径，AC为弦，OD⊥AC于D，过点O作OE∥AC交半圆O于点E，过点E作EF⊥AB于F，若AC=4，则OF的长为（　　）