题目

北师大研究团队发现自突触的兴奋传导机制，为深入揭示一些脑疾病的发病机理提供了新的思路。自突触只存在于中枢神经系统，是神经元的轴突与自身的树突或胞体形成的突触连接，如图所示，其中A、B、C为作用位点。下列叙述错误的是（ ）A.刺激A点时，细胞膜对钠离子的通透性大于钾离子B.刺激C点时，引起胞体反应的信号有电信号和化学信号C.为检测到自突触引起的突触后膜反应可选择切断B点D.自突触的形成具有细胞特异性，可降低神经元的反应根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有一项为多余选项。 Dear Sir, I have to travel every day from So UK Road to the airport. Two buses travel along this route: No.49 and No.16. However, by the time No.16 reaches So UK Road, it is always full.__1.__ The timetable states that there are buses from So UK Road to the airport every ten minutes.__2.__ The instructions state that if there are empty seats on a bus, the bus must stop at every stop where people are waiting. __3.__ The instructions state that no bus may carry more than 40 seated passengers and 20 standing passengers. Yesterday, I was the first to get off the bus when it reached the airport. __4.__ There were 129 of them. Clearly printed on the back of every bus is a sign that says “Maximum speed: 50mph.” ___5.__ Saturday morning a No. 49 bus traveled the distance in ten minutes, at an average speed of 60 mph. At times it must have done at least 80 or even 90 mph. It is obvious that our bus companies have neither respect for the instructions nor consideration for their passengers. Can nothing be done about this? Jerry A．I counted the other passengers as they got off. B．Why is it that half-empty buses go straight past me when I am standing at the bus stop? C．The problem is that we have to pay more for our trip. D．The distance from So UK Road to the airport is 10 miles. E. This leaves No.49 which sometimes has empty seats on it. F. If this is so, why do I have to wait half an hour for a bus nearly every day?