19. change one's mind　 v. 改变主意

18.　 altitude n.

(1)(海拔)高度 At high altitudes of Tibet it is difficult to breathe.

在西藏海拔很高的地方呼吸很困难。

(2)高处The plane flew at an altitude of 20000 metres.

飞机在两万公尺的高空飞行。

(3)地平纬度

17． Stubborn　 adj. 坚决的；坚定的； 倔强的

She won't do what I ask - she's very stubborn.

她不按我的要求去做，她很固执。

16. 　cycle

n. 周期, 循环, 自行车, 一段时间, 整套, (电学)周波

vi．循环, 轮转, 骑自行车

vt. 使循环, 使轮转

　　 Sunspots increase and decrease in intensity in an 11-year cycle.

太阳黑子以十一年为一个周期增强和减弱

He cycles to school every day．他每天骑车上学。

15．Finally　 adv.

　　 (1)最後，最终　 She finally agreed with me. 她最终同意了我(的意见)。

Their dispute has not finally settled yet.　 他们之间的争端尚未最终解决。

(2)不可改变地；决定性地　 It's not finally settled yet.　 那事尚未有决定性的解决。

参考词汇：at last,in time,finally,in the end

　 (1) at last 强调久等之后

When the fire had at last been put out,the forest authorities ordered several tons of special type of grass-seed which would grow quickly.

在大火终于被扑灭的时候，森林管理局订购了好几吨特殊速生草籽。

(2)in time 表示经过一段不定的时间之后

In time,all Sam's money was paid back in this way.

山姆所有的钱终于都用这种办法归还了。

(3)finally 也表示久等之后，但有时表示在一系列因素的最后一个之后

After putting it off three times,we finally managed to have a holiday in Greece.

推迟了三次度假之后，我们终于在希腊度了假。

　　 (4)in the end 和 finally 同义，但 finally 一般位于谓语前。这些词除 finally 之外，其他三个都可以用在谓语前，也可位于谓语后

In the end, we stay at home and look after everything.

最后，我们还是呆在家里照看着一切。

14． To climb the mountain road was hard work but to go down the hills was great fun. 上山很艰难，而下山却很好玩。

　　　　 to climb 和 to go down the hills 都是动词的不定式短语，在句中作主语用。

13． At last, the river’s delta enters the South China Sea. 最后，湄公河三角洲的各支流流入南海。

12．Once she has made up her mind, nothing can change it. 她一旦下决心，什么也不能使她改变。

　　　　 once 可以做状语从句的连词，意为“一旦”。如：

　 　　　Once you show fear, he will attack you. 你一旦显出害怕，他就会攻击你。

　　　　 Once you make a promise, you should keep it. 你一旦许诺，就要兑现。

　　　　 make up one’s mind 下定决心；拿好主意。如：

　　　　 I haven’t made up my mind yet. 我还没打定主意呢。

　　　　 He has made up his mind to go into business when he leaves college. 他下决心大学毕业以后经商。

11．She gave me a determined look-the kind that said she wouldn’t change her mind. 她给了我一个坚定的眼神-这种眼神表明她是不会改变主意的。

　　　 determined 在句中是个形容词，意为“坚定的，坚决的”。如：

　　　 His mother is a determined woman who always gets what she wants. 他母亲是一个坚定的女人，她总能达到自己的目的。

　　　 They were determined to drive the enemy from their land. 他们决心把敌人赶出他们的领土。

10. Although she didn’t know the best way of getting to places, she insisted that we find the source of the river and begin our journey there. 虽然她对去某些地方的最佳路线并不清楚，她却坚持我们要找到河的源头，并从那里开始我们的行程。

I insist that he (should) study medicine instead of law. 我坚持要他学医，不学法律。

Jack insisted that we (should) put our tent on the big rock. 杰克坚持我们把帐篷搭在那块大岩石上。

类似的动词还有determine, order, request等。