单项选择题
A．backache B．fever and coughing C．stomachache D．serious headache
A．if you live wherever there is Lyme disease B．when you go out gardening or walking C．if you are playing with your dog D．when you are traveling around
A．the United Nations thinks it possible to avoid a population explosion B．5.1 billion people are living in the underdeveloped countries C．in advanced nations the population growth is being controlled D．the world's population is increasin