**Core Concept**
Early childhood caries (ECC) or baby bottle tooth decay is a type of dental caries that affects children, typically caused by frequent and prolonged exposure to sugary substances. The primary concern is the premature loss of primary teeth, which can lead to various oral health issues and impact the child's overall well-being.

**Why the Correct Answer is Right**
The correct answer is based on the definition of early childhood caries. ECC usually occurs in children between 18 and 36 months of age. This age group is particularly susceptible to dental caries due to several factors, including the presence of primary teeth, limited dexterity for proper oral hygiene, and frequent consumption of sugary substances. The American Academy of Pediatric Dentistry (AAPD) defines early childhood caries as 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.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is close to the correct answer but does not encompass the entire age range associated with early childhood caries.

**Option C:** This option is partially incorrect as it includes the month "June" which is beyond the typical age range for early childhood caries.

**Option D:** This option is incorrect as it includes the month "December" which is also beyond the typical age range for early childhood caries.

**Clinical Pearl / High-Yield Fact**
It is essential for parents and caregivers to establish good oral hygiene habits in children from an early age, including regular brushing, flossing, and limited sugary snack consumption. The AAPD recommends that children should visit a pediatric dentist by their first birthday or within six months of the eruption of their first tooth.

**✓ Correct Answer: A. 18-36**