(1)In any vital city, a sidewalk has uses far beyond easing the passage of pedestrians. (2)Front steps facing the sidewalk are places for neighbors to sit and visit, just as corners are places to "hang out." (3)Sidewalk street life also serves as a means of public surveillance, through which people come to know each other and to identify strangers. (4)Sociologist Jane Jacobs points out that in areas where street life abounds, crime rates are low. (5)In addition, sidewalks are environments where children explore their neighborhood, test themselves, and grasp the rules of urban social life. (6)Finally, street life brings a sense of community to a neighborhood. (7)South Philadelphia, New York's Lower East Side, New Orleans's French Quarter, and San Francisco's Haight-Ashbury district all maintain a positive identity based on their street life.

Question1. Sentence 1 provides