题目

某商品以每包30千克为标准，32千克记为+2千克，那么记为-3千克、+5千克、-2千克、+1千克、+4千克的5包该商品的平均质量为                    （    ）A．31千克        B．30千克       C．1千克       D．5千克  答案：A解析:略  ----How do you usually go to work?---I often go to work __________. Walking is good for our health.A. by bike B. by busC. on foot D. by car