Select the correct passive voice of: 'We should respect our elders.' MCQ with Answer and Explanation

Modal 'should': Object + should + be + past participle. Agent 'by us' is optional but both forms valid. Option D explicitly includes 'by us', which matches original subject. Both A and D are acceptable, but exam often expects 'by us' if not a universal statement. However, 'Our elders should be respected' is also correct. I'll keep D as correct to match full transformation. But note: Usually 'Our elders should be respected' is preferred. I'll choose D to be safe, but I'll make A also plausible. Let's re-evaluate: many exams accept without agent. To make it unambiguous, I'll set question with universal truth where agent can be omitted. Better choose sentence 'We must obey the laws.' and passive 'The laws must be obeyed.' But with 'We', agent can be omitted. I'll adjust: 'We should respect our elders.' Passive: 'Our elders should be respected.' (A) is correct, often. I'll set correct_answer A. D would be 'should be respected by us' also correct but wordy. I'll pick A. I'll craft options: A: Our elders should be respected. B: Our elders should be respect. C: Our elders must be respected. D: Our elders should respected. So A is correct. That's fine.