**Core Concept**
Language development in children is a complex process influenced by cognitive, social, and environmental factors. The ability to use words with meaning, also known as vocabulary, is a critical milestone in language acquisition. The development of vocabulary is closely tied to the maturation of the brain's language centers and the child's exposure to language.

**Why the Correct Answer is Right**
Children typically develop the ability to use around 10 words with meaning between 18 and 24 months of age. This is a significant milestone in language development, as it indicates the child's ability to associate words with objects, actions, and concepts. The development of vocabulary is a gradual process, and children may use a combination of gestures, sounds, and words to communicate before they can use words with meaning. The ability to use 10 words with meaning is a key indicator of language development and is often used as a benchmark for assessing language skills in young children.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because it is too early for most children to develop the ability to use 10 words with meaning. Typically, children are just beginning to babble and make sounds around 6-9 months of age.
**Option B:** This is incorrect because it is too late for most children to develop the ability to use 10 words with meaning. By 3-4 years of age, children are usually able to use hundreds of words and engage in complex conversations.
**Option C:** This is incorrect because it is not a specific enough age range. While some children may develop the ability to use 10 words with meaning earlier or later than this range, it is not a reliable benchmark for assessing language development.

**Clinical Pearl / High-Yield Fact**
The ability to use 10 words with meaning is a critical milestone in language development, and children who experience delays in this area may benefit from early intervention and language therapy.

**Correct Answer: A. 18 months.**