题干

肉毒杆菌是一种致命病菌,在繁殖过程中分泌毒素。军事上常将这种毒素用于生化武器。人们食入和吸收这种毒素后,神经系统将遭到破坏。该毒素由两个亚单位(每个亚单位为一条链盘曲折叠而成)组成的一种生物大分子,下面是肉毒类毒素的局部结构简式,据此判断下列说法中不正确的是(   ) 
   

A:由结构图可知,肉毒类毒素由氨基酸组成,其化学本质是蛋白质

B:图中该片段由5种单体组成,有4个肽键

C:一分子肉毒类毒素至少含有1个氨基和1个羟基

D:高温下可使肉毒类毒素失活,主要原因是高温首先破坏蛋白质的空间结构

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C

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    At thirteen, I was diagnosed(诊断) with a kind of attention disorder. It made school difficult for me. When everyone else in the class was focusing on tasks, I could not.

    In my first literature class, Mrs. Smith asked us to read a story and then write on it, all within 45 minutes. I raised my hand right away and said, “Mrs. Smith, you see, the doctor said I have attention problems. I might not be able to do it.” She glanced down at me through her glasses, “You are no different from your classmates, young man.”

    I tried, but I didn't finish the reading when the bell rang. I had to take it home.

    In the quietness of my bedroom, the story suddenly all became clear to me. It was about a blind person, Louis Braille. He lived in a time when the blind couldn't get much education. But Louis didn't give up. Instead, he invented a reading system of raised dots(点), which opened up a whole new world of knowledge to the blind.

    Wasn't I the “blind” in my class, being made to learn like the “sighted” students? My thoughts spilled out and my pen started to dance. I completed the task within 40 minutes. Indeed, I was no different from others; I just needed a quieter place. If Louis could find his way out of his problems, why should I ever give up?

    I didn't expect anything when I handed in my paper to Mrs. Smith, so it was quite a surprise when it came back to me the next day—with an “A” on it. At the bottom of the paper were these words: “See what you can do when you keep trying?”