问题
单项选择题
动作电位的特点之一是（）。
A．阈下刺激，出现低幅度的动作电位
B．阈上刺激，出现较大幅度的动作电位
C．动作电位的传导随传导距离的增加而变小
D．各种可兴奋细胞动作电位的幅度和持续时间可以各不相同
E．动作电位可以总和
答案
参考答案：D
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动作电位的特点之一是（）。
A．阈下刺激，出现低幅度的动作电位
B．阈上刺激，出现较大幅度的动作电位
C．动作电位的传导随传导距离的增加而变小
D．各种可兴奋细胞动作电位的幅度和持续时间可以各不相同
E．动作电位可以总和
参考答案：D
I ran across an old photo of him the other day, thinking of some old things. He’s been dead for 25 years. His name was Rex. 1_____ was his favorite recreation(娱乐). He had so much 2_____ in the water as any person I have known. You didn’t have to throw a stick in the water to 3_____ him to go in. Of course, he would bring back a stick to you if you 4 _____ throw one in. That 5 ____ me of that night, 6_____ he brought back a small box that he found somewhere--- how 7_____ nobody ever knew. Since it was Rex, it 8_____ easily have been half a race. The box wasn’t a god one. It was just a 9______ old piece that somebody 10______. Still it was something he wanted, probably 11_____ there was some difficulty in transportation（运输）. And that he thought could test his courage. We first knew about his achievement when, deep in the night, we 12 _____ him trying to get the box up onto the porch(门厅). It sounded 13_____ two or three people were trying to tear the house 14 _____. We came downstairs and turned on the 15_____ light. Rex was on the top step trying to pull the thing up, but it had 16_____somehow. And he was just holding his own(坚持着). I suppose he would have held his own 17_____ dawn if we hadn’t helped him. The next day we carried the box miles away and threw it out. If we had thrown it out in a 18____ place, he would have brought it home again, as a small token(象征)of his strength in such matters. 19____, he had been taught to carry heavy wooden objects about and he was 20_____ of his skill. 小题1:1.
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