**Core Concept**
Early Childhood Caries (ECC) is a term used to describe the presence of one or more decayed (non-cavitated or cavitated lesions), missing (due to caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger. ECC is a significant public health concern due to its potential impact on a child's oral health and overall well-being.

**Why the Correct Answer is Right**
The correct answer of 71 months is based on the definition of Early Childhood Caries as proposed by the World Health Organization (WHO). This definition is significant because it helps dental professionals identify children at risk of developing ECC and implement preventive measures to reduce the incidence of this condition. The 71-month threshold is also important because it distinguishes ECC from other types of caries that occur in older children and adolescents.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not provide a correct threshold for defining ECC.
**Option B:** This option suggests a threshold that is too low for ECC, as children under 12 months of age are not typically considered at risk for ECC.
**Option C:** This option suggests a threshold that is too high for ECC, as children over 5 years of age are more likely to be at risk for dental caries due to other factors.

**Clinical Pearl / High-Yield Fact**
The American Academy of Pediatric Dentistry recommends that children visit a pediatric dentist by their first birthday to prevent ECC and promote good oral health habits.

**Correct Answer: B. 71 months.