题干

颜色变化常作为生物实验结果观察的一项重要指标,下面是一些学生在实验中遇到的问题,其中的错误操作或想法是
①用滴管在花生子叶薄片上滴加苏丹III染液,发现满视野都呈现橘黄色,于是滴1-2滴50%盐酸洗去浮色   
②取新鲜的菠菜叶,加少许SiO2和无水乙醇,研磨液呈黄绿色。于是判断是菠菜叶用量太少导致  ③在纸层析法分离叶绿体中色素的结果中,蓝绿色带最宽,可判断为叶绿素a含量最多   
④乳酸菌、酵母菌和蓝藻的细胞内都有核糖体和染色体
⑤测定绿色植物的呼吸作用时需在暗处进行,可避免光合作用对实验结果的影响

A:①②④⑤

B:①②④

C:②③④⑤

D:①③⑤

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A

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       Around four years ago, I received a call from the principal of our school as to the “Parents View” talk the next morning. He asked me to speak to the group. After the call, my whole body became feverish and panicky. The time from his call to the next morning seemed like years. The whole night, I could not sleep with many ominous_apprehensions in mind. One of them was to call the principal with regret and tell him that I could not come. Finally, I gathered some courage. I thought, “If I miss this opportunity, surely the school will never invite me again to any of their programs.”

       I reached the school in time. Before my turn came, my whole body was trembling. When my turn came and I started speaking, my heartbeat increased and my mouth went dry. I wasn't even able to read the written speech properly. I was not aware of where I was standing and what I was reading. That was the day when I realized my biggest weakness: Public Speaking.

       After my speech, I met with the principal and explained what happened to me. He told me that this happens to everyone. Even great speakers faced the same things when they started. He suggested that I come again next time.

       Around one month later,I was invited to refer to a topic on motivation. This time I was feeling comfortable. My speech was appreciated by the principal as well as the teachers, because I was able to get my idea across to them. They encouraged me and praised my efforts.

       After delivering it successfully, I became more confident. I said to myself,“If I can speak in front of such a learned audience, like the principal who educates others, I can now speak in front of others too.”

       I started delivering lectures on various topics like Self Motivation, Personality Development, Personal Excellence, Spoken English and Presentation Skills. This has become a passion for me. I have learned that everything is possible if we have the courage to take the first step.