To solve this problem, we need to determine the correct values of X and Y, where X is the total number of rib pairs in humans, and Y is the number of true rib pairs. Let's analyze the options:$\newline \bullet$Option 1: X = 12, Y = 5 - This is incorrect because there are 12 pairs of ribs, but only 7 pairs are true ribs.$\newline \bullet$Option 2: X = 24, Y = 7 - This is incorrect because there are 12 pairs of ribs, not 24. True ribs are not free on the ventral side.$\newline \bullet$Option 3: X = 24, Y = 12 - This is incorrect because there are 12 pairs of ribs, not 24. True ribs are not free on the ventral side.$\newline \bullet$Option 4: X = 12, Y = 7 - This is correct. Humans have 12 pairs of ribs, and the first 7 pairs are true ribs. True ribs are attached dorsally to the vertebral column and ventrally to the sternum.$\newline$Explanation:$\newline \bullet$Humans have 12 pairs of ribs in total.$\newline \bullet$True ribs (first 7 pairs) are attached dorsally to the vertebral column and ventrally to the sternum.$\newline \bullet$The remaining ribs are false ribs (8th to 12th pairs), with the 11th and 12th pairs being floating ribs, which are not attached to the sternum.$\newline$Therefore, the correct option is Option 4: X = 12, Y = 7.