Final answer:
The subject of this question is the ratio between carts and baskets at a B) grocery store.
Step-by-step explanation:
In this question, the subject is Mathematics. The question asks about the ratio of carts to baskets at a grocery store. The ratio is given as 3 to 1, which means that for every 3 carts, there is 1 basket.
The subject of this question is the ratio between carts and baskets.