Several Years Ago, Schoolchildren Began Mailing the Styrofoam Containers from McDonald's

Several years ago, schoolchildren began mailing the Styrofoam containers from McDonald's meals they had purchased back to McDonald's headquarters. The schoolchildren wanted McDonald's to stop using Styrofoam and instead use biodegradable packaging, which the company did. From an economic perspective, the schoolchildren were pressuring McDonald's to

A) increase the supply of nutritional meals.
B) create a positive externality.
C) compete fairly with other fast-food chains.
D) reduce their negative externality.
E) reduce global warming.