轨道结构主要由()四部分组成,应具有足够的强度、稳定性、耐久性和适量弹性。
A、钢轨
B、联结零件
C、道床
D、道岔
E、轨道电路
参考答案:A, B, C, D
用括号内所给词的适当形式填空。(10分)
My new school 小题1: (be not) near my home. It’s quite a long way. Let me 小题2: (tell) you how I get to school every day. Every morning, I have to 小题3: (get) up early at half past five. I 小题4: (leave) home at six and take the train from our town into the city. It takes an hour 小题5: (get) to Central Station. Then I take the subway to East Cross Station. From there I 小题6: (walk) to school in about ten minutes. I usually arrive at school at eight.
Today I woke up late, so I 小题7: (have) to take a taxi. Tomorrow I plan 小题8: (get) early, and my father小题9: (take) me to school. How do you get to school every day? Write to me soon and 小题10: (tell) me about it.
某有机化合物A含碳77.8%,氢为7.40%,其余为氧,A的相对分子质量为甲烷的6.75倍.求:
(1)该有机物的分子式.
(2)红外光谱测定,A分子结构中含有苯环和羟基,能与烧碱反应,且在常温下A可与浓溴水反应,1molA最多可与2molBr2作用,据此确定该有机物的结构简式.