题干

用同位素14C标记的吲哚乙酸来处理一段枝条的一端,然后探测另一端是否含有放射性14C的吲哚乙酸存在。枝条及位置如图,下列有关处理方法及结论的叙述正确的是(   )

A:处理甲图中A端,不可能在甲图中的B端探测到14C的存在

B:处理乙图中A端,能在乙图中的B端探测到 14C的存在

C:处理乙图中B端,能在乙图中的A端探测到14C的存在

D:处理甲图中B端,能在甲图中的A端探测到14C的存在

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答案(点此获取答案解析)

C

同类题5

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    On a rainy night three years ago my dear mom went to accompany her Lord. She did it her way.

    I got the call at work, and l headed home quickly. Mom and Dad lived on a small farm that they had owned since I was seven. I hated going there every weekend. There was nothing for a young girl to do but watch the one station on the old TV set, if the weather allowed reception.

    My mom, on the other hand, loved the peace and quiet of the land. The place was rural, with no indoor plumbing or heat. We had a big wood stove in the kitchen that did its best to heat the little farmhouse, but it always seemed cold and too quiet to me.

    In the evenings, my mom and I would sit for hours singing in the little kitchen. I sang the melody and Mom harmonized. Her favorite song was “Moon River” and we sang it over and over. Mom told me stories about how when I was a little girl I could sing before I could talk.

    As time passed, I had my own children and went to visit them every week or two. The kids loved the farm and the tractor rides with my dad. Me, well, I still hated the silence of the farm. While my mom loved to sit at her kitchen table and look out at her garden and flowers and retell all the old stories, I missed the hustle and bustle of my life at home. But I sat there listening quietly as she reminisced.

    Now, I sat back in the silence and the silence was deathly so I finally leaned over to turn on an old radio. Music always comforted me. My heart skipped a beat. “Moon River” was playing on the radio. I sat there wordless, with a tear running down my cheek, as I listened to every familiar note.