题目

Mr. Brown is a teacher. He is from New York, America. He would like（想）to work in China because he likes our country. He thinks Chinese people are very friendly and he likes to live in China. He is happy to work in our school. He likes the school life here. He teaches English. There are 50 students in his class. Mr. Brown is kind. He and his students are good friends, too.Now some of Mr. Brown’s students play sports on the playground（操场）. Bill and Mike play tennis. Tom and John play ping-pong. The other students play basketball. Mr. Brown is happy to play basketball with them. T温度为500℃时，反应4NH3+5O2?4NO+6H2O在5L的密闭容器中进行，半分钟后NO的物质的量增加了0.3mol，则此反应的平均速率（x）为（ ）A．（O2）=0.025mol?L-1?s-1B．（NO）=0.06mol?L-1?s-1C．（NH3）=0.002mol?L-1?s-1D．（H2O）=0.03mol?L-1?s-