【单选题】

{{I}} Questions 11-13 are based on the following conversation. You now have 15 seconds to read the questions 11-13.{{/I}} Which of the following exercises is suggested

A、Wearing arm weights while you are swimming.
B．Jogging vigorously in one place for a long time.
C．Using bicycles that require you to use both your arms and legs.
D．Walking slowly while swinging your arms back and forth.