①缩小生产规模 ②遵循价值规律
③立足市场需要 ④坚持诚信经营
A:①②
B:①③
C:②③
D:②④
——Where do you often exercise?——I often exercise in a park. It's close to my house.
鲫鱼是一种常见的淡水鱼类.关于“探究鲫鱼适应水中生活特征”的实验结论,正确的是( )