Many People Bring Empty Containers to Recycling Centers

Many people bring empty containers to recycling centers. What does this mean in terms of contributing to a sustainable society?

A) Recycling metal and glass reduces the energy that would otherwise be used to produce the finished products from raw materials.
B) Recycling metal and glass reduces the energy that would otherwise be used to extract, refine, and transport the raw materials.
C) Recycling is insignificant relative to the size of current environmental problems, but it makes people feel that they are making a contribution.
D) Both a and b are correct.