B

    We all need to exercise. Doctors say it is good for us. It makes our heart and body strong. It also gives you more energy(能量). And you will feel better about yourself. It's best to exercise twice a week. Twenty minutes each time is enough.

    There are many ways to exercise. You can walk, run, play sports or swim. Many people go to special places to exercise. They are called "fitness centers". These places have a lot of equipment(设备). Some people buy equipment for their homes. But it's very expensive.

    Exercising can be fun. Friends can exercise together at fitness centers. Or they can play sports together. How do you exercise? How often do you exercise?

将一片新鲜的植物叶片放入装有70℃温水的烧杯中，发现叶片的背面冒出的气泡比正面多，这说明(    )

现有下列物质：熟石灰、碳酸钠、氯化钠、碳酸钙、碳酸氢钠、氢氧化铝、稀盐酸等，在生产、生活中有广泛的用途．请按下列要求填空：

①农业中用来降低土壤酸性，改良土壤结构的是____ ；②可治疗胃酸过多的是____ ；③用于造纸、玻璃、印染、洗涤剂的是____；④用于维持人体正常生理活动的是____ ；⑤天安门前的汉白玉华表的主要成分是____ ；⑥可消除公路积雪的盐____．

张老师家2016年5月的购买衣物支出400元．