（1）小华看到爸爸用电热水壶烧水泡茶，他马上由此联想到几点包含在其中的物理知识，请你帮小华说出两点：① ____；② ____

（2）密度计是用来测量液体密度的仪器，它的构造如图所示，一根密闭的玻璃管，上部粗细均匀，标有刻度；下部较粗，底部B处装入小铅粒．把密度计放入待测液体中，待其静止后，保持竖直漂浮状态（密度计底部不可碰到容器底部），由与液面相平的刻度可以读出被测液体的密度．从密度计的结构、原理或使用方面，试说出两点有关的物理知识．

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判断下列句子是否正确,正确的写“正确”,错误的写“错误”

    The school library opening time is from 8: 00 to 16: 00. Students must remember （记住）that they must not bring food and drinks into the library. They can take out six books every time. And they can only keep them for one week. If they don't give back the books on time, they'll have to pay（支付） some money. Students must take care of all the books. But some books are only for teachers.