Experts predict that if current trends continue, by 2050, over 70% of the world's population *will have been residing* in urban areas, a significant shift from historical demographics.

✓ Correct Answer: Option C

The future perfect continuous 'will have been residing' incorrectly implies an ongoing action completed by a future point. The simple future 'will reside' is more direct and appropriate for a projected state or completion by a future time.