Final answer:
The Moro reflex is the infant reflex that uses sound and movement for protection and survival, involving the infant spreading out arms, pulling them in, and crying when feeling like they are falling.
Step-by-step explanation:
The infant reflex that utilizes sound and movement for protection and survival is the Moro reflex. This reflex is an instinctive behavior present from birth until about three to four months of age. It's triggered by a sudden loss of support, which might make the infant feel like it is falling. The Moro reflex includes a sequence of actions: the infant suddenly spreads out the arms, pulls them back into the body, and usually cries. This could potentially help the baby to reach out and grab hold of its mother or another caregiver, thus promoting survival.
Another important reflex is the grasping reflex, where a baby will instinctively grasp any object that is placed into the palm of their hand. It is already present at birth and persists until about five to six months of age. It is hypothesized that this reflex could have helped infants in the past to cling to their mothers, increasing the infant's chances of survival.