A:刺激神经纤维中部,产生的兴奋沿神经纤维向两侧传导
B:兴奋在神经纤维上的传导方向是由兴奋部位至未兴奋部位
C:神经纤维的兴奋以局部电流的方式在神经元之间单向传递
D:在神经纤维膜外,局部电流的方向与兴奋传导的方向相反
飞行的炮弹击中目标后有很大的破坏作用,这是因为 ( )
These are Cara and Ben. They are twins (双胞胎). They are twelve. This is their bedroom. It's a nice room. There are two beds in the room. The yellow bed is Cara's and that green one is Ben's. The twins have one desk and two chairs. The chairs look the same. Cara's sweater is on his bed. Ben's coat is on his chair. Their clock, books and pencil-boxes are on the desk. Their schoolbags are behind the chairs.