Explanation:

- India’s southern neighbours across the sea include island countries in the Indian Ocean.

- These countries are often recognized as part of maritime South Asia and include Sri Lanka, Maldives, and sometimes others depending on broader definitions.

- Option 1: Three - This includes Sri Lanka, Maldives, and potentially another group or territory some might consider.

- Option 2: Four - More countries or regions would need to be considered beyond the typical recognition.

- Option 3: Five - This option does not match the most common geographical recognitions.

- Option 4: Two - This refers to Sri Lanka and Maldives as the primary island nation neighbors across the sea.

Correct Answer: Option 1 - Three