Read the article and select the best answer. Article: winter-swimming has become popular in Beijing. three years ago, few people would go swimming in the city waters. but now there is a winter-swimming enthusiasts'club and it has more than 2,000 members. the oldest is 84 years of age and the youngest is only 7. _ They may be workers, peasants, soldiers, teachers, students....Though it is now the coldest part of the season and the water temperature in the city's lakes is around 0degc, many winter-simmers still swim in the icy waters, even when it is snowing. They enjoy themselves in the lake, while the people by the side of the lake are wearing heavy clothes. why are so many people interested in winter-swimming? Because winter-swimming can be good for one's health. Bei Sha is a good example. He is 69 years old, and he once suffered from heart trouble for 26 years. After ten years of winter-swimming he is now in good health. Scientists are now studying the effects of winter-swimming on health. Question: Winter-swimming has become popular in Beijing because _ . Options: A: more and more people like to swim in winter B: it is more interesting than swimming in summer C: winter-swimmers are brave men D: winter-swimming does a lot of good to one's health
D