The following sentence has been divided into parts. One of them may contain an error.
For the last three years, Sunita had been running private hostels near this university.

Correct option is A

Option (a) contains an error.
Explanation: The expression "for the last three years" indicates time continuing till present, which should be in the Present Perfect Continuous Tense, not the Past Perfect Continuous Tense.
Hence, "had been running" should be replaced with "has been running".
Correct sentence: For the last three years, Sunita has been running private hostels near this university.
Grammatical rule used:
· Use Present Perfect Continuous (has/have been + V1+ing) for actions that started in the past and are still continuing.
· Use Past Perfect Continuous (had been + V1+ing) when referring to an action before another action in the past.
Example:
· He has been working here since 2020.
· He had been working there before he shifted to Delhi.