化学是一门以____ 为基础的自然科学，他研究物质的____ 、____ 、____ 及____ 等．学习化学，既可提炼出自然界里____ 的物质，还可制造出自然界里____ 的物质．

由绵阳出发到成都的某一次列车，运行途中须停靠的车站依次是：绵阳→罗江→黄许→德阳→广汉→清白江→新都→成都.那么要为这次列车制作的车票一共有（　　）

如图是某动物精子形成过程中的一组细胞示意图．请回答下列问题：

（1）图①所示的细胞处于减数第____ 次分裂，此时细胞内有____ 对同源染色体．

（2）没有姐妹染色单体的细胞是图____ 和____ 　，该动物体细胞内有____ 条染色体．

     A good way to pass an exam is to work hard every day in a year. You may fail in an exam if you are lazy for most of the year and then work hard only a few days before the exam. If you want to be good at English, you have to read stories in English, and to speak English as much as possible. A few days before the exam you should go to bed early. Do not go to bed late at night. Before you start answering in the exam, read carefully over the question papers, and try to understand the meaning of each question. When you have finished your exam, read over your answers. Correct the mistakes and be sure that you don't miss anything out.