The correct answer is D. He prayed that God would grant peace to the departed soul.
A. He wished by God to grant peace to the departed soul.
This is incorrect because the speaker is not wishing for God to grant peace to the departed soul, but is praying for God to do so.
B. He wished that God may grant peace to the departed soul.
This is incorrect because the speaker is not expressing a wish, but is making a prayer.
C. He prayed that might God grant peace to the departed soul.
This is incorrect because the speaker is not using the subjunctive mood, which is typically used to express wishes or possibilities.
D. He prayed that God would grant peace to the departed soul.
This is the correct answer because the speaker is using the indicative mood, which is typically used to express facts or realities. The speaker is praying for God to grant peace to the departed soul, and is expressing a belief that God will do so.