Based on this information, the nurse documents that the infant has:

The correct answer is C: Severe dehydration. The infant's presentation of dry mucous membranes, sunken fontanelle, and poor skin turgor are indicative of severe dehydration. This is a critical finding that requires immediate intervention to prevent complications. Failure to thrive (A) refers to inadequate weight gain and growth, not dehydration. Malabsorption syndrome (B) is characterized by difficulty absorbing nutrients, not dehydration. Risk for fluid volume deficit (D) implies potential but does not confirm dehydration.