**Core Concept:** Moro's reflex is a primitive reflex that occurs in infants during intrauterine life. It is a sudden, brief, and exaggerated startle response to sudden stimuli, characterized by the infant lifting its head, bending the knees, and extending the arms. This reflex is a normal part of an infant's development and should cease to occur by a specific age.

**Why the Correct Answer is Right:** Moro's reflex is a physiological response that plays a vital role in survival during intrauterine life. It helps infants to orient towards a sudden stimulus and protects them from potential harm. In healthy infants, this reflex is normal and should diminish gradually over time as they develop motor skills and cognitive abilities. The correct answer (C) refers to the age of 4-6 months, which is a typical time when infants begin to exhibit signs of cognitive and motor development, such as grasping objects and sitting unsupported.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect as Moro's reflex is a normal physiological response during intrauterine life. While it might persist beyond 4-6 months, it is not considered abnormal unless it causes significant distress or developmental delay.

B. This option is incorrect as Moro's reflex is a normal response during intrauterine life. Although it may persist beyond 4-6 months, it is not considered abnormal unless it interferes with the infant's ability to adapt to the postnatal environment or causes significant distress.

D. This option is incorrect as Moro's reflex is a normal physiological response during intrauterine life. Although it may persist beyond 4-6 months, it is not considered abnormal unless it causes significant distress or developmental delay.

**Clinical Pearl:**

Moro's reflex is a normal and essential part of an infant's development, helping them to orient towards sudden stimuli and protect themselves during intrauterine life. It is crucial to differentiate between normal persistence of Moro's reflex and its persistence causing distress or developmental delay. If the reflex persists beyond the typical age range of 4-6 months, it should be evaluated by a pediatrician and further assessment may be required if it interferes with the infant's adaptation to the postnatal environment or causes significant distress.