when you go to the groccery store and they ask you paper or plastic, which is the better choice?

I think that's one area where certain shops are actually improving. Most offer reusable fabric bags or plastic bins, and both are way better options than paper or plastic bags in the long run. To answer your question, I think paper and plastic are both bad choices, opt instead to purchase (or make!) a couple fabric bags. They're convenient, reusable, and they keep thousands of plastic bags out of our already packed landfills.