Mark the letter A, B, C, or D to indicate the sentence that best completes each of the following exchanges.Câu hỏi Nam: “What do you personally do to keep fit?”Lan: “ __________.” A. I think keeping fit is necessary for everyone. B. As far as I know, more and more people exercise to keep fit. C. Fitness centres are mushrooming. D. I just do morning exercise and maintain a balanced diet.