Concept: Linguistics is the scientific study of language, focusing on how human language is structured, used, and understood.
Explanation: Language is a natural part of human society. Most people learn their mother tongue before adulthood without formal study. Linguistics examines this everyday ability in detail.
It looks at how sounds combine to form words, how words form sentences, and how sentences carry meaning. Linguists also study sign languages and written scripts.
The field covers all aspects of human language: sounds (phonetics), word structure (morphology), sentence structure (syntax), and meaning (semantics).
Linguistics does not focus on teaching methods like Direct Method or Grammar-Translation Method. Those are approaches to language teaching, not the subject of linguistics itself.
Answer: D. Human language