A. The flow of blood to the muscles. B. Classical conditioning. C. Protein interaction. D. Stimuli through the cells. 参考答案:C 答案解析:[分析] 本题为细节题。参见第二段谈及肌肉运动的解释“...changes in the membrane of muscle cells;entry of particular chemicals;
第21题: [单项选择]In English many nouns can be turned into verbs without any change to their form. For instance, the noun walk can be turned into the verb to walk. This phenomenon is known as ______ in morphology. A. compounding B. derivation C. conversion D. inflection 参考答案:C