题目

右图为一突触结构模式图。下列相关叙述中，正确的是 A.刺激b 点，bc 段膜外电流方向为b→c B.刺激b点，c、d同时兴奋 C.刺激b点，a、c均会兴奋 D.刺激b 点，只会引起B 神经元兴奋 答案：C Such plants never ________ in this part of the world． [　　] A． have grown B． are growing C． grow D． are grown