The correct option is B Femur
In humans, each limb is made of 30 bones. The bones of the legs (hind limb) are femur (thigh bone, the longest bone), tibia and fibula, tarsals (ankle bones 7 in number), metatarsals (5 in number) and phalanges (digits 14 in number). A cup-shaped bone, called as patella covers the knee ventrally (knee cap).