218. naval a. 海军的
The naval port is silent and beautiful at night.军港之夜寂静而美丽。
219. navigation n. 航行
Navigation Acts航海条例
220. necessity n. 必需品;必要性
Food and clothing are necessities of life.食物和衣服都是生活的必需品。
221. previous a. 先，前，以前的 He has had no previous experience of this kind of job.他从前没有做这种工作的经验。
222. provision n. [pl.]给养，口粮
Provisions are plentiful.粮食充足;设备，装置;准备 They make provision against possible disasters.他们采取措施防备可能发生的灾难。
223. pursue vt. 追逐 ，追求，从事，进行
The police are pursuing an escaped prisoner.警方正在追捕一个在逃的犯人;
People can not live only to pursue pleasure.人不能只为寻乐而活着;
She pursued the study of English for five years.她持续不断地学了五年英语。
224. stale a. 不新鲜的，陈腐的
stale bread不新鲜的面包，stale news陈旧的资讯
225. substitute n. 代用品 vt. 代替
Use plastics as a substitute for steel.用塑料做钢的代用品;
If you cannot go yourself, please find someone to substitute you.如果你不能亲自去就找个人代你去。
(搭配)substitute for代替...，替换...， 取代...;substitute sth. [sb.] for用某物[某人]来代替