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. Every summer about a dozen journalists gather at a former army training camp north of London to spend the day watching the training of London's special armed police unit.
    每年夏天，总有大约十几名记者聚集在伦敦北部的一个旧军训营，用一整天来观看伦敦特警部队的训练。

3. We put up our tent in the camp site.
    我们在营地上搭起了帐蓬。

4. While Alfred´s little army slowly began to gather at Athelney, the king himself set out to penetrate the camp of Guthrum, the commander of the Danish invaders.
    阿尔弗雷德人数不多的军队开始在阿塞尔纳慢慢集结时，他亲自潜入丹麦入侵司令官古瑟罗姆的营地。

5. Tazieff was able to set up his camp very close to the volcano while it was erupting violently.
    当火山正在猛烈地喷发时，塔捷耶夫有办法把帐篷搭在离它非常近的地方。

6. The camp itself consisted of little more than hammocks strung between trees, the fires to keep off the jaguars, and half a dozen cooking pots.
    他们的营地设备只有拴在树间的吊床，防范老虎的篝火和五六只炊锅。

7. 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。

8. Now, dressed in a blue uniform and with a rifle over his shoulder, the prisoner marched boldly up and down in front of the camp.
    现在他身穿蓝军装，肩扛步枪，在军营门前大胆地来回走看。

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

10. He could hear shouting in the camp itself.
    他能听到营房里的喧闹声.