已知C—C键可以绕键轴自由旋转，结构简式如下的烃，下列说法中正确的是( )
A．分子中至少有8个碳原子处于同一平面上
B．分子中至少有9个碳原子处于同一平面上
C．该烃的一氯取代物最多有8种
D．该烃是苯的同系物
答案：B
题目分析：甲基与苯环平面结构通过单键相连，甲基的C原子处于苯的H原子位置，所以处于苯环这个平面．两个苯环相连，与苯环相连的碳原子处于另一个苯的H原子位置，也处于另一个苯环这个平面，另一苯环所用的C原子都处于同一平面上，至少有1个碳原子与另一个苯环同平面，所以至少有9个碳原子共面，故B正确，A错误；每个苯环上4个H各不相同，取代苯环上的H有4种异构体，再加上甲基被取代，则该烃的一氯取代物最多有5种，故C错误；该有机物含有2个苯环，与苯在组成上不相差-CH2的倍数，且不饱和度不同，不是苯的同系物，故D错误；所以本题的答案选择B。
点评：本题考查了有机物的结构及其性质，该题对学生的分析能力要求有点高，本题难度中等。
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| A man who knows how to write a personal letter has a very powerful tool. A letter can be enjoyed, read and 1 . It can set up a warm conversation between two people far apart (远离的); it can keep a 2 with very little effort. I will give 3 . A few years ago my older brother and I were not getting 4 . We had been close as 5 but had grown apart. Our meetings were not 6 ; our conversation was filled with arguments and quarrels; and every effort to clear the air seemed to only 7 our misunderstanding. Then he 8 a small island in the Caribbean and we 9 touch. One day he wrote me a letter. He describe his island and its people, told me what he was doing, said how he felt, and encouraged me to 10 . Rereading the letter, I was 11 by its humor (幽默) and clever expressions. These were all qualities for which I had 12 respected my order brother but 13 he no longer had them. I had never known he could write so 14 . And with that one letter we became friends 15 . It might never have occurred to 16 to write me if he had not been in a place where there were no 17 . For him, writing was a necessity. It also turned out to be the best way for us to get back in touch. Because we live in an age of 18 communication (通讯), people often 19 that they don't always have to phone or email. They have a 20 . And that is to write. | ||||
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