The correct answer is:
b. show avoidant attachment are least distressed by their mother’s departure, while infants who display ambivalent/resistant attachment are severely distressed when they are separated from their mothers.
In attachment theory, avoidant attachment is characterized by a lack of distress when the caregiver leaves and avoidance of the caregiver upon return. In contrast, ambivalent/resistant attachment is characterized by high levels of distress when the caregiver leaves and difficulty settling down even upon the caregiver's return.