Final answer:
The scale of the map is 1 centimeter = 3 kilometers, given that 4 centimeters on the map represent an actual distance of 12 kilometers.
Step-by-step explanation:
The distance between the library and the grocery store on the map is 4 centimeters, and the actual distance is 12 kilometers. To find the scale of the map, you divide the actual distance by the map distance. So, you divide 12 kilometers by 4 centimeters, which gives you 3 kilometers per centimeter.
Therefore, the scale of the map is 1 centimeter = 3 kilometers, which corresponds to option A.