Why is it, when shoppers go to the grocery store, the store offers customers either plastic or paper bags to carry their groceries home in?

because plastic creates more pollution but is cheaper

In my opinion the word reason here is RENEWABILITY/SUSTAINABILITY.

Explanation: Renewability and Sustainability are both synonyms and can be defined as the ability for something to be produced or sustained for a long period of time without damaging the environment or without depleting a resource. Modern plastic shopping bags are increasingly recyclable or biodegradable. modern bags are made of vegetable-based bioplastics, which can decay organically and prevent a build-up of toxic plastic bags in landfills and the natural environment.

option number one would be youre best option