下面是最早发现青霉素时弗莱明所进行的探索过程．

观察及对问题的认识：细菌培养基中偶然生出青霉菌，在其周围无菌生长．为什么出现这种现象？

提出假设：____ ．

进行实验：把青霉菌放入培养基中培养观察，然后观察这种培养基对细菌生长的影响．实验实验结果：这种培养基阻止了细菌的生长和繁殖．

结论：弗莱明先生在持续的研究中分离出了这种抑菌物质，分析出它的化学结构并将它命名为青霉素．

说明：在实验室里培养细菌、真菌常用琼脂配置成凝胶，平铺在培养皿作为培养基，某些细菌需要添加特殊的培养基才能正常生长．

请回答：

（1）作为这一实验的下列假设中，最为恰当的是____ ．

A．青霉菌能产生有利于人类的物质

B．青霉菌污染了细菌生长的培养基

C．青霉菌可能吞噬了细菌

D．青霉菌可能产生了不利于细菌生长繁殖的物质

（2）为了证明青霉素确实是青霉菌产生的而不是培养液和培养基中的其他物质引起的，则应设计对照实验，方法是____ ．

（3）若对照实验结果为____ ，则充分证明了____．

    SPECIAL EVENTS THIS WEEKEND

    Captain Good Fellow

    Do your children enjoy interesting stories, funny games, and exciting dances? Captain Good Fellow will be ready to teach all these things to children of all ages at the City Theatre on Saturday morning at 10:00, Free.

    Walking Tour of the Town

    Forget your worries on Saturday morning. Take a beautiful walk and learn about local history. Meet at the front entrance of City Hall at 9:30. Wear comfortable shoes!

    Films at the Museum

    Two European films will be shown Saturday afternoon at the Museum Theatre. See Broken Window at 1:30. The workers will be at 3:45. For further information, call 4987898.

    International Picnic

    Are you tired of eating the same food every day? Come to Central Park on Saturday and enjoy food from all over the world. Delicious and not expensive. Noon to 5:00 pm.

    Take Me out to the Ballgame

    It's October, and tonight is your last chance to see the Redbirds this year. Get your tickets at the gate. It might be cold；don't forget sweaters and jackets.

Do You Want to Hear “The Zoo”

     “The Zoo”, a popular rock group from Australia, will give their first US concert tomorrow night at 8:00 at Rose Hall, City College.

我们常见的自然现象是水往低处流，而植物体内的水则往高处移动，水向高处移动的动力来自（    ）

地球上的海洋，被陆地分割成彼此相连的四个大洋，分别是____ 、____ 、____ 、____ ，其中，面积最大的是____ ．