**Core Concept**
The eruption time of primary and permanent teeth is a crucial aspect of pediatric dentistry and orthodontics. The eruption time of permanent teeth varies among individuals, but it is influenced by genetic and environmental factors. The eruption of mandibular lateral incisors is a significant event in dental development.

**Why the Correct Answer is Right**
The eruption of mandibular lateral incisors typically occurs between 8 to 12 years of age, with a mean age of 9-10 years. This timing is influenced by the completion of the root formation of the first permanent molars and the second premolars. The eruption of these teeth is a sign of the transition from mixed dentition to permanent dentition. The mandibular lateral incisors develop from the dental lamina and are influenced by the growth and development of the mandible.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the eruption time of mandibular lateral incisors is not typically between 5 to 7 years of age, which is the range for the eruption of the first permanent molars.
**Option C:** This option is incorrect because the eruption time of mandibular lateral incisors is not typically between 12 to 15 years of age, which is the range for the eruption of the second premolars.
**Option D:** This option is incorrect because the eruption time of mandibular lateral incisors is not typically between 15 to 18 years of age, which is the range for the eruption of the third molars (wisdom teeth).

**Clinical Pearl / High-Yield Fact**
The eruption time of permanent teeth can be influenced by various factors, including genetics, nutrition, and environmental factors. A delay in the eruption of permanent teeth can be a sign of a systemic condition, such as hypothyroidism or celiac disease.

**Correct Answer: C. 9-12 years.**