Which of the following options is the most suitable conversion of the following sentence into Passive Voice?
People believed that he was innocent.

Correct option is C

The correct option is (c).

Explanation:
The given sentence is in the Active Voice with a complex structure (Subject + Verb + that-clause). When a sentence begins with 'People believe/believed...', it is converted into passive voice using the introductory 'It'. Since the main verb 'believed' is in the Simple Past tense, the passive structure follows: It + was + past participle (V3) + that-clause.

Structure:
Active voice: Subject + V2 + that + clause
Passive Voice: It + was + V3 + that + clause

Why other options are incorrect:
Option A uses 'will believe' (future), which changes the tense. Option B and D use 'believe' (V1) instead of the past participle 'believed', making them grammatically incorrect. So the correct answer is (c)