Select the most appropriate proverb/idiom that can substitute the highlighted segment in the given sentence.
After his repeated warnings went unheard, the teacher decided to stop trying to discipline the unruly students, realising that it is useless to offer advice to someone who refuses to listen.

Correct option is A

The correct option is (A).

Explanation: Option (A) is the correct meaning of the highlighted segment.
You can lead a horse to water, but you can't make it drink: This proverb means that you can give someone an opportunity or advice, but you cannot force them to take it or act upon it. (आप किसी को अवसर दे सकते हैं पर उसे लाभ उठाने के लिए मजबूर नहीं कर सकते)
Example: I showed him all the research, but he still bought the faulty car; I guess you can lead a horse to water, but you can't make it drink.

Other related idioms and their meanings:

• A leopard cannot change its spots: A person's character, especially a bad one, will not change.
• Empty vessels make the most noise: People who know the least often talk the most.
• A rolling stone gathers no moss: A person who does not settle in one place will not accumulate wealth or responsibilities.