Bharat Bhavan is architecturally distinctive for being a low, terraced building that steps down a hillside and blends into the landscape using local materials like terracotta tiles, so matching that design language to each architect's known style settles the question.
Only Correa's known design philosophy, low-rise, terrain-hugging, contextually rooted architecture, matches Bharat Bhavan's actual built form.
Therefore, the correct answer is Charles Correa.