Ratatouille is a Stew. Option A is the correct one
It is a dish which is based with tomatoes upon which sauteed garlic, onions, zucchini, bell peppers, fennel, basil, bay leaf, thyme and some herbs are being put. It is a french dish. and is widely liked by people in Europe.
There are many ways of making this dish, but most common method that mostly people use is the one mentioned above.