动作电位沿单根神经纤维传导时，其幅度变化是（）
A.逐渐增大
B.逐渐减小
C.先增大，后减小
D.先减小，后增大
E.不变
参考答案：E
Listen ! Do you hear someone _____ for help ?
A calling B call C to call D called
Don’t worry about ,Mom. I can take care of ..
A．I; me
B．I; myself
C．me; I
D．me; myself
