单项选择题A．Have a balanced diet, fresh air, sunshine, enough rest and regular exercise.B．Visit the doctor and go to hospital regularly.C．Spend enough time watching others exercising at home or in a stadium.D．Realize the importance of physical and mental health.

单项选择题A．Various forces outside the sender or receiver that make them unable to communicate.B．Various difficulties that a listener or receiver can experience when they have a cold.C．Various forces within a sender or receiver that cause them less able to communicate.D．Various reasons that can cause a person unable to take full advantage of his talents.