酪氨酸酶存在于正常人的皮肤和毛囊等处的细胞中，它能促使酪氨酸转变为黑色素，若编码此酶的基因发生了突变将导致白化病，这种现象说明

根据达尔文提出的自然选择学说，下列有关长颈鹿进化过程的解释，正确的是：（　　）

①长颈鹿的祖先有的颈长，有的颈短

②在缺乏青草的环境中，长颈鹿的颈经常使用而长长

③逐代选择，长颈的变异逐代积累形成长颈鹿

④通过生存斗争，颈长的个体生存下来，颈短的个体被淘汰

⑤在缺乏青草的环境中，颈长的长颈鹿容易获得食物而生存下来，颈短的则生存机会小．

完形填空
    As a teenager, I am often asked what I am going to be in the future. A lawyer? A doctor? Or a scientist? No, my ideal career is to be a teacher. One of the 1for that is I want to be a teacher like Mr. Chen.
    "Look! Do you know what it is? A-ha, it's the  2 ! And it will always move around the sun."Mr. Chen said and pointed to his head. He then touched the nose and 3 , "Can you tell me the name of this mountain? It is the highest mountain on Earth! What's the  4of it? Yes, it's 8844.43 metres…" I'll never forget my first geography lesson. He was  5 humorous that we all fell in love with his lessons   6. It's Mr. Chen who opened the door of geography for us.
    Generally speaking, most of the teachers are strict7students and sometimes a little bit demanding（苛求的）, not so with Mr. Chen. He is a lighthouse, showing us the way to the treasure of knowledge. He is a friend and easy to get  8 with, always encouraging us to speak out loud without 9our shyness and other disadvantages. He is an example, volunteering his time to students and other teachers.
     One day I happened to meet him in the hospital. Seeing the cut on his arm, I realized he was donating his 10. I was moved and was  11 another lesson, a lesson of love and devotion.
    Every time I see my globe（地球仪）, it would 12me of Mr. Chen. He is the most unforgettable teacher I have 13met and he will always be. Someday I hope I am  14  to be a teacher like him.
    Thank you, Mr Chen, thank you for making learning not a job but a joy.
    Thank you for helping me to discover what I do best and to do it even  15Thank you for understanding all of us and giving us the time and care each of us needs.

条件反射的建立提高了人和动物适应环境的能力，一旦形成就不会消失．（判断对错）

阅读下文，回答相关问题。

                                                                                                                                                   剥 豆
　　一天,我与儿子相对坐着剥豌豆，当翠绿的豆快将白瓷盆的底铺满时，儿子忽地离位新拿一个瓷碗放在自己面前，将瓷盆朝我面前推推。
　　看他碗里粒粒可数的豆，我问：“想比赛？”
　　“对”。儿子眼动手剥，利索地回答。
　　“可这不公平，我盆里已不少了，你才刚开始。”我说着顺手抓一把豆想放在他碗里。
　　“不，”他按住我的手：“就这样，我才能试出自己的速度。”
　　一些喜悦悄悄在我心里散开。
　　一时,原本很随意的家务劳动有了节奏，只见手起豆落，母子皆敛声息语。
　　“让儿子赢，使他以后对自己多一些自信。”如是想，手不知不觉就慢了下来，俯拾豆的机会稍停一下。
　　“在外面竞争是靠实力。谁会让你？让他知道，失败成功皆是常事。”剥豆的速度分明快了。
　　小儿手不停，眼却时时在两个容器中睃。见他如此投入，我心生怜爱：学校的考试名次，够他累的了……剥豆的动作不觉中又缓了下来。
　　“不要给孩子虚假的胜利。”节奏自然又紧了许多。
　　一大袋豌豆很快剥光。一盆一碗、一大一小不同的容器难以比较，凭常识，我知道儿子肯定输了，正想淡化结果，他却极认真地新拿来了碗，先将他的豆倒进去，正好满一碗，然后又用同样的碗来量我的豆，也是一碗，只是凸出了，像隆起的土丘。
　　“你赢了。”他朝我笑笑，很轻松，全没有剥豆时的认真和执著。
　　“是平局。我本来有底子。”我纠正他。
　　“我少，我就是输。”没有赌气，没有沮丧，儿子认真和我争。脸上仍是那如山泉般清澈的笑容。
        细想起来，自己瞻前顾后，小心翼翼，实在是多余了。