A child arrives for physical therapy due to a burn from a hot liquid. The physical therapist is assessing for depth of penetration to classify the burn using capillary refill. The therapist presses down on the skin for 4 seconds and then watches how long it takes for the burn to regain color. The therapist notes that the burn has a mottled white appearance and does not blanch with pressure. How does the therapist classify this burn?

a) superficial burn
b) superficial partial thickness burn
c) deep partial thickness burn
d) full thickness burn