While evaluating the reflexes of a newborn, the nurse notes that with a loud noise the newborn symmetrically abducts and extends his arms, his fingers fan out and form a "C" with the thumb and forefinger, and he has a slight tremor. The nurse would document this finding as a positive:

Choice A rationale The Babinski reflex is assessed by stroking the sole of the foot from the heel up and across the ball, which should cause the toes to curl downward (plantar flexion) in a normal infant. A positive Babinski sign in an adult (toes fanning out) indicates neurological impairment, but in a newborn, a transient fanning and dorsiflexion of the big toe is often a normal finding due to immature central nervous system myelination. This is not the reflex described. Choice B rationale The Glabellar reflex (or blink reflex) is elicited by gently tapping the newborn's forehead or glabella (the skin between the eyebrows). A positive response involves the newborn blinking in response to the tap. This is a brainstem-mediated, protective reflex that persists throughout life. It is tested to assess neurological integrity but is unrelated to the described startle reaction with arm and hand movements. Choice C rationale The Moro reflex, also known as the startle reflex, is a primitive reflex typically present from birth to about 6 months of age. It is triggered by a sudden loud noise or loss of head support. The characteristic response involves symmetrical abduction and extension of the arms, fanning of the fingers with the thumb and forefinger forming a 'C' shape, followed by adduction of the arms, sometimes accompanied by a tremor, exactly as described. Choice D rationale The Tonic neck reflex (or fencing posture) is observed when the infant's head is turned quickly to one side while they are supine. The reflex involves the arm and leg on the side to which the head is turned extending, and the opposite arm and leg flexing. This is a different, posture-regulating reflex, unrelated to the sudden startle response described by the nurse.