Final answer:
The Upanishads were passed down orally from teacher to teacher to maintain their sacredness.
Step-by-step explanation:
The correct answer is A) Orally, diminish.
The Upanishads were passed down orally from teacher to teacher for thousands of years. It was believed that writing the texts would diminish their sacredness. This oral transmission ensured that the texts were preserved in their original form and maintained their sacred value.
For example, students would sit at the feet of their teachers and listen to the teachings, memorizing and reciting the Upanishads to ensure their accurate preservation.