Solution:The given sentence is in past continuous tense associated with passive voice.Look at the structure of active and passive voice of past continuous tense.
Passive voice: Passive subject + was/were + being + V³ + by + Passive Object.
Sharn was being taught by Anil.
Active Voice: Subject (object of passive voice) + was/were + V⁴ + object (subject of passive voice).
Anil was teaching Sharan.