Convert the sentence below from active voice to passive voice:

Will the board approve the revised proposal promptly?

The correct option is Will the revised proposal be approved promptly by the board?

Step-by-step conversion from active to passive voice:

1. Identify the structure of the active sentence:
The given sentence is an interrogative sentence in the simple future tense:
"Will (Auxiliary Verb) + the board (Subject) + approve (Main Verb) + the revised proposal (Object) + promptly (Adverb)?"

2. Rule for converting Simple Future interrogative sentence to passive voice:
Active form: Will + Subject + Verb (base form) + Object?
Passive form: Will + Object + be + Verb (past participle form / V3) + by + Subject?

3. Apply the transformation:
• Object becomes the new subject: the revised proposal
• Auxiliary verb structure for simple future passive: will + be
• Past participle (V3) of "approve": approved
• Agent: by the board
• Retain adverb: promptly

Putting it all together yields:
"Will the revised proposal be approved promptly by the board?"