A. It was known to him that his own life had been unjust.
B. It was known by him that his own life was unjust.
C. It was known to him that his own life was unjust.
D. It was known by him that life was unjust.
Given sentence is in simple past tense and it is in active voice.
Rule :
Subject + (was/were) + V3 + Other agents
