Out of ____'X'_____ pairs of ribs in humans only _____'Y'_____ pairs are true ribs. Select the option that correctly represents values of X and Y and provides their explanation.

	X	Y
1	12	5	True ribs are attached dorsally to vertebral column and sternum on the two ends
2	24	2	The true ribs are dorsally attached to vertebral column but free on ventral side.
3	24	12	True ribs are dorsally attached to vertebral column but free on ventral side
4	12	7	True ribs are attached dorsally to vertebral column and ventrally to the sternum