A 3-day-old male infant born at 40-weeks gestation is being evaluated for breastfeeding latch. The mother notices that he seems vigorous and wakes to feed, but it appears he has difficulty staying latched onto the nipple. Once he initiates breastfeeding, the latch is painful, and the mother notes that her nipples have become raw and tender. She does not think her milk is in yet since the baby has only had one wet diaper in the last 24 hours. As the nurse assesses the newborn's mouth, he notices that when the baby cries, the tongue appears slightly heart-shaped, and the lingual frenulum appears shortened. What is a likely cause of the breastfeeding problem described here?
A. Epstein's pearls
B. Caput succendaneum
C. Soft palate cleft
D. Tongue-tie