Final answer:
The equation that describes the direct proportional relationship between the amount of sand, s, in pounds, and the number of concrete stones, c, is given by option (A) s = 4c, which implies that each stone requires 4 pounds of sand.
Step-by-step explanation:
The relationship between the amount of sand (s) in pounds and the number of concrete stones (c) depends on their proportional association. If one concrete stone requires a specific amount of sand, and this relationship is constant, then the amount of sand used is directly proportional to the number of concrete stones made. Option (A) s = 4c suggests that for every concrete stone, there are 4 pounds of sand used. This is a direct representation of a linear relationship, where the amount of sand increases uniformly with the number of stones.