A 6-month-old male presents with 2 days of vomiting and diarrhea. He is conscious, but his level of activity is decreased. The infant's mother tells you that he has not had a soiled diaper in over 12 hours. The infant's heart rate is 140 beats/min and his anterior fontanelle appears to be slightly sunken. You should suspect:

A. mild dehydration.
B. moderate dehydration.
C. severe dehydration.
D. hypovolemic shock.

Answer: B. moderate dehydration.