名词
1. concentration是什么意思
1. Concentration is essential if you want to do a good job.
如果你想把事情做好，专心是必要的。
2. What is the concentration of salt in sea water?
海水中盐的含量是多少？
3. This thesis will need all your concentration.
这篇论文需要全神贯注才能读懂。
4. There is a concentration of people in big cities.
大城市人口集中。