A 2-week-old infant who has had no immunizations，sleeps 18 hours a day，weighs 3.5kg，he takes 60ml of standard infant formula four times a day with no solid food and no iron or vitamin supplements.Of most concern is
A
Immunization status
B
Caloric intake
C
Iron levels
D
Levels of vitamins A、C and D
E
Circadian rhythm