Stick a stamp on an envelope before you put it into the mail-box.
把信投进信箱前在信封上贴上邮票。
The key(was) stuck in the lock. 钥匙卡在锁里了。
stick 还可以和几个介词或副词构成词组，如：stick at顾虑，stick out突出，stick together彼此忠诚友爱 等等。本课中stick to是“坚持”的意思。又如：
After the marriage, the couple will stick to each other all their lives.婚礼之后，夫妇将终生厮守在一起。
They stuck to the experiment until they got the satisfactory result.他们坚持实验直到得到满意的结果。
18. From that time on Einstein was greatly respected as the leading scientist of the century.从那时起爱因斯坦被尊崇为本世纪最杰出的科学家。
1) respect常常被用作普通及物动词，或被用于respect sb. for sth.或respect sb. as sth两种结构，前者表示“因为什么而尊敬某人”，后者表示“将某人作为什么来敬重”。如：I wish people would respect my privacy. 我希望人们尊重我的隐私权。
respect也可以被用作名词，意为“尊敬”“敬意”或“方面”。如：
The prime minister is held in the greatest respect. 首相备受拥戴。
2) from that time on 意为“自从那时起”，常与过去时连用。注意since that time/since then/ever since then 也表示“自从那时起”，但它们必须与完成时连用，如：
From then on, he began to read the newspapers and magazines in French.
从那时起，他开始阅读法文报纸和杂志。
3) leading是lead(领导)的现在分词，在句中作scientist的定语，意为“主要的”


或“杰出的”，又如：
Who is the leading actor in the film? 片子的男主角是谁?
19. He had taken Swiss nationality in 1901 and therefore did not have to join the army, as Switzerland did not take sides in the war. 他在1901年加入瑞士国籍，因此可以免于参军，因为瑞士是中立国。
1) nationality一词来自nation-national, 意为“国籍”，提问时常用what, 如：
-What\'s your nationality? -你是哪个国家的?
-I\'m German. -我是德国人。
2) therefore是副词，意为“因此”，注意它与so有所区别，so既是连词，也是副词，而therefore是副词，在引导并列句时需加and，或者单列大写，如：
It rained yesterday, and therefore we had to put off our football match.
It rained yesterday；therefore we had to put off our football match.
It rained yesterday. Therefore we had to put off our football match.
3) take sides(with sb.)/take the side(of sb.)意为“同意、偏袒、支持(某人)”，如：
We were careful not to take sides for fear of getting into trouble.
我们留心不偏袒某一方，以免陷入麻烦。
20. What he wanted to see was an end to all the armies of the world. 他所希望的是取消世界上所有的军队。
1) what he wanted to see 是名词性从句作主语，如：What I saw was quite different from what I had heard. 我所见到的与我所听到的大相径庭。
2) end在本句中是名词，意为“终极”，如：
The story came to an happy end. 故事的结局美满。
21. When Germany was ruled by Hitler in the early 1930\'s, Einstein, who was a Jew, found it impossible to continue living in Germany. 20世纪30年代早期，德国处于希特勒控制之下，作为犹太人的爱因斯坦发现不能继续在德国住下去了。
1) rule在本句中是动词，意为“统治”。rule还可以作为名词使用，意为“规则”或“统治”，如：It\'s against the rules to handle the ball in soccer. 在英式足球中用手传球是违反规则的。