A College Student Walks Down New York City's Fifth Avenue

A college student walks down New York City's Fifth Avenue at 8:00 AM. She is late for class so she catches the bus for the last 2 miles of her commute. Did she have a larger ecological footprint when she was walking or when she was on the bus?

A) on the bus, because it is using energy to move
B) on the bus, because the road took more energy to build than the sidewalk
C) walking, because she is using energy that must be replaced by eating foods that are not locally grown
D) walking, because she is moving on a sidewalk that took energy and raw materials to build
E) More information is needed about, for example, the number of people on the bus and its fuel source, to accurately determine her ecological footprint in both situations.