**Core Concept**
The Moro reflex, also known as the startle reflex, is a primitive reflex that appears in infants. It is characterized by a distinctive movement of the arms and hands in response to a sudden, loud noise or a feeling of falling. This reflex is an important indicator of neurological development and maturation.

**Why the Correct Answer is Right**
The persistence of Moro's reflex beyond the age of 6 months is considered abnormal because it indicates a delay in the maturation of the central nervous system. Normally, the Moro reflex disappears by 4-6 months as the infant develops better motor control and integration of sensory inputs. The persistence of this reflex suggests a possible neurological issue or a delay in cognitive development.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Moro reflex typically disappears by 4-6 months, and persistence beyond this age is abnormal. However, there is no clear consensus on the exact age cutoff.
**Option B:** This option is incorrect because the Moro reflex may still be present in some infants at 12 months, but this is not considered abnormal in all cases. The key is to assess the individual infant's developmental progress and determine if the reflex is persistent or not.
**Option C:** This option is incorrect because the Moro reflex is not typically considered abnormal until it persists beyond 6-9 months. However, this is still a general guideline, and individual cases may vary.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the disappearance of the Moro reflex is a crucial milestone in infant development, and its persistence beyond 6 months may indicate a need for further evaluation and assessment.

**Correct Answer: C. 6 months**