题目

大肠杆菌在繁殖时，细胞内钾离子的浓度是培养液的3000倍。如果在培养液中加入一种叫箭毒素的药物，大肠杆菌细胞内钾离子浓度立即下降，这种药物很可能 A．使细胞膜变成全透性                          B．抑制膜上载体的活动 C．加快细胞膜的流动                             D．使载体运动方向改变 --- Is your good friend _____ China now?--- Yes, he is. He likes China very much.A. at B. of C. in D. for