Hello, I'm Jack. I live in a house. My address is 246 Second Street. It's far from the school. So I go to school by bus every day. But my house is near the park. So I often go to the park on foot. Tom is my friend. He lives in a house, too. It is near the school. So he goes to school on foot every day.

①遵守社会公德，提高自身素质        ②提倡文明出游，做到遵纪守法

③减少外出旅游，维护自身形象        ④学会自我保护，掌握旅游知识

从20名学生中随机抽取一名，若抽中女生的概率是$\frac{2}{5}$，则这20名学生中有女生____ 名．