The language which is learnt from environment without any explicit teaching is

The correct option is First language.

Explanation:

First Language (Mother Tongue / Native Language):
A person's first language is acquired naturally during early childhood from their immediate social environment (family, caregivers, community). This process is known as language acquisition, which occurs implicitly without any formal instruction or explicit teaching.

Why other options are incorrect:
• Second language / Third language: These are typically learned after the primary language is established, often through formal education, structured courses, or intentional practice (known as language learning).
• School language: This is the medium of instruction used in educational institutions, which requires explicit teaching of grammar, vocabulary, reading, and writing skills.