材料：
蚂蚁身上的抗生素
美国细菌学家卡梅隆·柯里在《科学》杂志发表了研究论文，声称从5000万年前开始，以真菌为生的蚂蚁就有了自己的抗生素。研究者对一种名叫“真菌蚂蚁”的蚂蚁身上的白色斑点进行研究，发现不同“真菌蚂蚁”依靠种植不同的真菌类蘑菇来作为唯一的食物来源。这些蚂蚁的嘴巴和前肢上隐藏着许多细小的腺窝，里面寄生着一种能产生抗生素的细菌。这些腺窝有一些细小的孔通向蚂蚁身体外部，这样它们就可以将抗生素传播给作物。抗生素可以杀死会使作物生病的寄生虫，从而确保它们主人的食物来源不受破坏。
这种蚂蚁腺窝的特殊结构使得蚂蚁与作物的这种共生关系非常和谐。研究者发现，一些近缘的不种植真菌的蚂蚁身上则没有腺窝，也没有寄生菌。
科学家们研究了中美洲热带丛林中的切叶蚁的生活习性。切叶蚁只种一种蘑菇，这相当于人类的单一作物制，虽然开始时产量高，但重复种几季以后很容易遭受病虫害侵袭，人类是采用轮作不同作物来解决问题的。生物学家们采用基因分析法，确定了切叶蚁所种的菌种是源于2300万年前的单一菌株，从未换过品种，却能延续至今。
这个谜由多伦多大学的C·R·居里解开了。居里对包括切叶蚁在内的22种蚂蚁进行了仔细观察。他首先发现蚂蚁的蘑菇农场偶尔也会受到一种名为Es-covopsis的霉菌感染，使蘑菇在几天内全部死光，结果是整穴蚂蚁全部饿死。但尽管如此，切叶蚁还是有办法控制这种灾难。其奥秘在于.雌蚁会排出寄生在身上的活细菌分泌出的链霉素。切叶蚁蘑菇园中那些忠于职守的蚂蚁勤于察看，一发现Es-covopsis霉菌就用随身携带的链霉素就地将之消灭，以防止其蔓延。而且这种链霉素还能刺激蘑菇的生长，真是一举两得。切叶蚁分群时，蚁后将蘑菇菌种含在口中，连同随身的会分泌链霉素的细菌带到新穴传种，所以切叶蚁的单一品种的蘑菇农场能延续至今，历经千万年而不衰。人类所用的抗生素多次使用后会使病菌产生抗药性而导致药效减弱.但蚂蚁所用的抗生素却并未使病菌产生抗药性。卡梅隆·柯里研究小组发现，蚂蚁身上的抗生素不但是蚂蚁赖以战胜自然环境的法宝，亦是人体必需的抗生素，今后应可仿此研发新一代的抗生素.更有效地治愈人类的疾病。
Many people invest in the stock market hoping to find the next Microsoft and Dell. However, I know (21) personal experience how difficult this really is. For more than a year, I was (22) hundreds and sometimes thousands of dollars a day in investing in the market. It seemed so easy, I dreamed of (23) my job at the end of the year, of buying a small apartment in Paris, of traveling around the world. But these dreams (24) to a sudden and dramatic end when a stock I (25) , Texas cellular phone wholesaler, fell by more than 75 percent (26) a one-year period. On the (27) day, it plunged by more than $15 a share. There was a rumor that the company was (28) sales figures. That was when I learned how quickly Wall Street (29) companies that, in one way or another, misrepresent the (30) .
In a (31) , I sold all my stocks in the company, paying (32) margin debt with cash advances
A. winner
B. champagne
C. genius
D. mentor
It is the duty of every man to work. The life of a lazy man is (21) to himself or to others. The man who is too (22) to work is the man who is generally most ready to beg or to steal. Everybody (23) he is young should learn some useful work.
But it is not (24) He should put his heart and soul completely (25) his work, and not waste his spare time. "Work while you work and play while you play." is as good a (26) for young people as for old.
There is (27) help to diligence than the habit of early rising, and this, just like (28) good habits, is most easily formed in (29) . There is an English proverb "Lost time never retums." This (30) everybody must be diligent, and must make good use of his (31) . One must study hard when one is young, (32) one may make (33) progress, succeed in life and become useful to one’s country and p
A. or
B. for
C. and
D. so that
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