题目

Teachers have to constantly update their knowledge in order to maintain their professional________． A．consequence       B．independence C．competence        D．intelligence 答案：C哺乳动物体内明显具有增殖能力的细胞为（     ） A．神经细胞     B．皮肤的基底层干细胞     C．肝细胞    D．肌肉细胞