某密闭容器内有X、Y、Z、W四种物质，在一定条件下充分反应，测得反应前后各物质的质量如表：

下列说法正确的是（   ）

用显微镜观察“生物”二字，显微镜下看到的图形应该是下列哪种情况（　　）

阅读下面短文，从短文后每小题的四个选项中选出能填入相应空白处的最佳选项

      Sports are very important. People from different parts of the world enjoy sports. Sports are 1 for people's health. Some people like to play sports games by themselves, but some 2 watching others play sports games. They buy tickets or 3 their TV to watch games.

      Sports 4 with the four seasons. People would like to play 5 games in different seasons. Most people's favorite sports are swimming and skating. Swimming is in summer and skating is usually in6. Sometimes they play inside the room. Sometimes they play outside. Some people play sports for 7 and fame while others just play for fun.

     We can 8 sports here and there. Some sports are so 9 that people everywhere like them a lot. Football, for example, is very popular all over theworld. People 10 different countries can't understand each other, but after a game they often become very friendly to each other.