Under the treaty signed in May 2025, the United Kingdom agreed to hand sovereignty of the Chagos Archipelago to:

Correct answer: (d) Mauritius

Explanation

The UK will transfer the Chagos Archipelago to Mauritius, while the UK–US base at Diego Garcia stays under a 99-year lease. The UK separated the islands from Mauritius in 1965 and leased Diego Garcia to the USA in 1966.