In ancient Indian society, education was not merely the transmission of information but a deeply respected cultural and spiritual endeavor. The teacher—known by titles such as guru, ācārya, or upādhyāya—was seen as a person of immense spiritual and moral stature.
The word "guru" itself comes from Sanskrit where "gu" means darkness and "ru" means remover. Thus, a guru was considered someone who removes the darkness of ignorance and leads the student to enlightenment or knowledge. This is what the Reason (R) expresses.
Teachers in the Vedic and later classical traditions did not simply teach subjects like grammar, logic, medicine, or philosophy—they shaped the minds and characters of students. Education was personalized and often imparted in residential schools (gurukulas), where students lived with the teacher and imbibed values through both instruction and observation. Teachers were given the utmost reverence by students and society alike. In many cases, they were placed on a pedestal equal to or higher than one’s own parents.
This cultural background makes the Assertion (A) completely valid. The Reason (R) provides the very philosophical foundation for why the teacher was so highly honoured—it wasn’t just for their subject knowledge, but for their spiritual role in a student’s life.
Therefore, both Assertion and Reason are true, and Reason correctly explains the Assertion.