Facial nerve stimulation during testing of nerve indicated by contraction of which muscle?: (A) Temporalis, (B) Masseter, (C) Sternocleidomastoid, (D) Orbicularis oris
Answer is D. Facial nerve supplies the muscles of the facial expression like orbicularis oris. 
Muscles of mastication like masseter and temporalis are supplied by the mandibular nerve, a branch of trigeminal nerve.
Spinal accessory nerve supplies sternocleidomastoid and the trapezius.