In the book of Joel, a plague of locusts devastates the land. Beyond the literal destruction, what does Joel emphasize as the primary purpose of this plague?

A To serve as a catalyst for national repentance and a return to God among the people of Judah. B To punish the surrounding nations for their idolatry and wickedness. C To enrich the land with nutrients from the locusts' bodies, leading to a more abundant harvest in the future. D To demonstrate God's power over nature, proving His superiority to pagan deities.