A. ‘War and Peace’ was written by Leo Tolstoy.
B. ‘War and Peace’ is written by Leo Tolstoy,
C. ‘War and Peace’will be written by Leo Tolstoy.
D. ‘War and Peace’ was being written by Leo Tolstoy.
Given sentence is in simple past tense and it is in active voice, we need to change it into passive voice.
Rule :
Subject + (was / were) + V3 + Optional Agents.