Answer:
A. Growth faltering
Explanation:
Six-month-old Luka's weight, height, and head circumference are substantially below age-related growth norms. Luka is withdrawn and apathetic. Luka's mother sometimes appears depressed and distant, at other times impatient and hostile. Luka most likely suffers from growth faltering.
Growth faltering is used to refer to a slower rate of weight gain in childhood than expected for age and sex.