【答案解析】With the improvement of living standards (As living standards improve), people are becoming increasingly aware of the importance of health. On the one hand, physical and mental health contribute to longevity; on the other hand, health largely (to a great extent) determines the quality of life and success in one's career. Although people think differently about (have different ideas about) which form of exercise is the best, they all agree that regular exercise, optimism (positive thinking), a pollution-free environment and strong marriage are the keys to keeping fit.