A 3-Month-Old Female Develops Colicky Pain, Abdominal Distention, and Diarrhea

A 3-month-old female develops colicky pain, abdominal distention, and diarrhea after drinking cow's milk. The best explanation for her symptoms is:

A) a deficiency of bile that stimulates digestive secretions and bowel motility.
B) an excess of amylase, which increases the breakdown of starch and causes an osmotic diarrhea.
C) an overgrowth of bacteria from undigested fat molecules, which leads to gas formation and decreased bowel motility.
D) an excess of undigested lactose in her digestive tract, resulting in increased fluid movement into the digestive lumen and increased bowel motility.