Which grammatical structure is essential for expressing a hypothetical condition in the past that did not happen, along with its hypothetical past result, often used in IELTS to discuss missed opportunities or regrets?

✓ Correct Answer: Option C

The Third Conditional is specifically used to talk about hypothetical situations in the past that were contrary to fact, and their imagined consequences. This demonstrates a higher level of grammatical complexity and accuracy suitable for higher IELTS band scores.