The biceps femoris has two heads as its name implies. Each head has its own nerve supply. The long head is innervated by the tibial branch of the sciatic nerve (L5, S1, S2, and S3). The short head is innervated by the peroneal branch of the sciatic nerve (L5, S1, and S2). Thus answer 1 is the correct choice.
Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, Philadelphia, PA, Lippincott, 1977
Jenkins DB (ed): Hollinshead’s Functional Anatomy of the Limbs and Back, ed 6, Philadelphia, PA, WB Saunders, 1991