1. Ethanol is more effective at a concentration of 50-70 per cent;
    乙醇的浓度为50%至70%时比较有效，

2. The not too surprising result was that the children whose parents were simply supportive were happier than average but were not particularly intense in their concentration when studying or working on something.
    结果并不太意外。支持型父母的孩子所感到的快乐程度高于平均水平，但学习或做事时却不是那么高度集中精力。

3. He has great powers of concentration.
    他注意力很集中。

4. I smoked with concentration and pleasure as I was sure that this would be my last cigarette.
    我聚精会神而又愉快地吸着这枝烟。因为我确信这是我最后一枝烟了。

5. Flying in combat and managing the complex weapons system requires considerably more concentration.
    在战争中驾驶并控制好那些复杂的武器系统则需要更加地专心。