题目

神经纤维的某一部位受到刺激产生兴奋时细胞膜外的电位变化是      A．由负变正    B．由正变负     C．不变，均为正电位    D．不变，均为负电位 答案：B14．A．Why didn't you go to see the film yesterday？B．What are you going to talk about at the meeting？C．How can I improve my reading skills？