Which one of the following is the best example of repeated falls in sea level, giving rise to present-day extensive marshland?

The Rann of Kutch is the correct answer because it is a vast saline marshland formed by tectonic uplift and repeated marine regressions (falls in sea level) that transformed a former shallow arm of the Arabian Sea into land. While Bhitarkanika Mangroves are also marshy, they are primarily the result of riverine sediment deposition (progradation) in an estuarine delta rather than sea-level fluctuations. The core concept being tested is marine regression and its role in shaping coastal geomorphology.