对小麦、玉米、向日葵等被子植物进行分类，往往以（　　）作为分类的重要依据．

    I like school days. I can learn many things from school. We have four classes in the morning and two in the afternoon. I like weekends, too. We don't go to school on Saturdays and Sundays. I often play ping-pong and play basketball on Saturday morning. I often play the violin (小提琴) on Saturday afternoon. I often do homework and play football on Sunday morning. I often go to the park on Sunday afternoon.

十八届四中全会提出，全面推进依法治国，总目标是建设中国特色社会主义法治体系，建设社会主义法治国家。全会提出，建设中国特色社会主义法治体系，必须坚持立法先行，发挥立法的引领和推动作用。深入推进科学立法、民主立法，完善立法项目征集和论证制度，健全立法机关主导、社会各方有序参与立法的途径和方式，拓宽公民有序参与立法途径。此次全会提出的法治中国建设是坚持依法治国、依法执政、依法行政共同推进，坚持法治国家、法治政府、法治社会一体建设的综合工程，并且包括了科学立法、严格执法、公正司法、全民守法在内的全过程。

结合上述材料，运用政治生活的相关知识，说明***、立法机关、人民政协和公民应如何深入推进科学立法、民主立法？

人和动物的皮肤属于(  )