单项选择题
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
A．suitable for people at any age B．lined with no side effects C．used to protect all people D．a safe and effective way to prevent Lyme disease