法国启蒙思想家孟德斯鸠在评价中国某一制度的作用时指出:中国没有世袭的官吏和贵族,皇帝通过考试等途径选拔官吏。凡是具有真才实学的人,不论出身如何,都有经过考试成为官吏的机会。该制度  (    )       

“夜已深，人不静，家家户户闪着灯；妇女灯下做棉衣，千针万线不放松；男人碾米又磨面……天寒心里热腾腾；为打胜仗人人忙，前后拧成一股绳……”这首民谣反映出解放战争迅速取胜的一个重要原因是（    ）

    Finding out what kind and how much physical activity you need

    How do I do it?

    It's your choice. Pick an activity that's easy to fit into your life. Do at least 10 minutes of physical activity at a time. Choose aerobic activities that work for you. These make your heart beat faster and can make your heart, lungs, and blood vessels fitter. Also, do strengthening activities which make your muscles do more work than usual.

    Why should I be physically active?

    Physical activity can make you feel stronger and more alive. It is a fun way to be with your family or friends. It also helps you improve your health.

    How many times a week should I keep physically active?

    It is up to you, but it is better to spread your activity throughout the week and to be active at least 3 days a week.

    How do I build up more physical activity?

    Do a little more each time. Once you feel comfortable, do it more often. Then you can trade activities at a moderate level for vigorous ones that take more effort. You can do moderate and vigorous activities in the same week.