17. nature n. 自然；自然界
keep the balance of nature
词性拓展： natural adj. 自然的； naturally adv. 自然的
用法拓展：against nature 违反自然 by nature 生来；天生 in nature 性质上；
in the nature of 具备……的性质
注意：nature 意思是“自然，自然界”，前面不加冠词。
16．Crazy adj. 疯狂的；狂热的
用法拓展： (1)be crazy about …….对…… 狂热，痴迷
(2)be crazy for sb./sth. =long for 渴望某物或迷恋某人
(3) be crazy with 因……而发疯
He has greatly improved is spoken English by learning Crazy English. And he ________ a chance to go abroad.
A. is crazy about B. is crazy for C. is hoping for D. hopes about
15．Outdoors adv. 在户外；在野外；
Children usually prefer playing outdoors.
相关拓展：outdoors adj.户外的，野外的
indoors adv. 在室内；入室内 indoor adj. 室内的
14. series n. 连续；系列
There will be a series of football games next month.
用法拓展：a series of meeting /exams /textbooks
two series of stamps
series单复数同型，作主语时谓语动词根据 series 单复数概念决定，不根据of 的名词决定。
13．German n. 德国人；德语 adj. 德国的；德国人的；德语的
词性拓展：Germany n. 德国
用法拓展：German 的复数形式是Germans, 而英国人、法国人的复数形式是Englishmen和Frenchmen.
12. Netherlands n. 荷兰 Netherlander n. 荷兰人
Netherlandish adj. 荷兰的；荷兰人的；荷兰语的 n. 荷兰语
11． Feeling n. 感觉；感情
词性拓展：feel vt./vi. 感觉，感受，触摸 feelings 情感
10．Share vt./vi.分享；共同使用 n. 一份；份额
用法拓展：
(1)share (in) sth. 分享/分担某物
(2) share sth. with sb. 与某人共享某物；与某人分担某物
9.list vt. 列出 n. 表，一览表，目录，名单
用法拓展：make a list of ……列……表
8．reason n. 理由；原因 vt./ vi. 推理；说服
e.g.: My reason is that the cost will be too high. 我的理由是费用太高。
词性拓展：reasonable adj. 合情合理的
(1)for this /that /no /some reason 因为这个/那个/没有/某一理由
(2)reason with sb. 和某人辩论
(3)by reason of 因为，由于……
(4)the reason for sth./ doing sth. is that …….做某事的理由是…….
(5) The reason why …… is that …… 做某事的理由是……
The reason _________ he was late was ______ his car had broken down on the way.
A. why; because B. that; because C. that; for D. why; that
She would like to know the reason ________ fewer and fewer students are showing interest in her lesson.
A. for B. why C. for that D. which
What do you think of the reason ________ he explained in his last letter ________ refusing the job?
A. why; why B. that; for which C. which; for D. that; because
(D. B.首先分析定语从句结构，主谓齐全，空格只能填状语成分，所以使用关系副词why; C改为for which 也对； C. 注意：reason 后面的定语从句不一定用why引导，要看在定语从句中缺少什么句子成分。在这里explain 缺少宾语只能用关系代词that 或 which 引导。
补充：reason 与cause 的区别
reason 指在事实的基础上通过逻辑判断出的理由与conclusion (结论)相对，常与for或why 连用；cause是自然造成某种结果的原因，与effect(结果)相对，常与of 连用。
用reason, cause 填空
(1) The ________ of the fire is still not known.
(2) Give me your ________ for doing it.