Active-to-passive voice (simple past): Convert the sentence to the correct passive while preserving tense and agent. Source sentence: James Watt discovered the energy of steam. Instruction: Choose the grammatically correct passive-voice option.

Given data

• Tense: simple past.
• Active: James Watt discovered the energy of steam.

Concept / Approach
Passive in simple past: was/were + past participle.

Step-by-step transformation
Object → subject: the energy of steam → The energy of steamAuxiliary: wasPast participle: discoveredAgent: by James WattFinal passive: The energy of steam was discovered by James Watt.

Eliminate wrong options
A: Misordered active-like structure; ungrammatical meaning. ❌B: Correct passive in simple past. ✅C: Nonsensical reversal of roles. ❌D: Changes tense and adds by the steam; incorrect. ❌

Final Answer
The energy of steam was discovered by James Watt.