《中国近代民族经济发展史》一书记载：“1912年日本输华商品总值只有9000多万两白银，1919年增至2．4亿两；美国从1913年的3500多万两，增至1919年的1．1亿两。日本由原来在列强对中国的经济中占第六位上升到与首位的英国势均力敌；美国在华的地位也举足轻重。”以下对这段材料反映的情况理解不正确的是（    ）

一头奶牛重500千克，一头河马的体重是奶牛的6倍，河马重（　　）吨。

化学家在当今环境问题上的最新构想是“变废为宝，资源循环”。例如，燃料 燃烧产物 燃料，这样既可解决能源问题，又能消除污染。上述构想中两个转化过程的变化为( )

    Tom always can't sleep well at night. But he was never late for work. He went to see his doctor on Sunday afternoon. He took the subway to get there. He met his boss on the subway and they talked for a while.

    Tom got some sleeping pills from the doctor. That night Tom took the pills. He had a nice sleep. He went to work happily on foot in the morning. Getting into the office, he said to his boss “I had a nice sleep and got up happily this morning.” “That's fine,” shouted the boss, “but where were you on Monday?”