Explanation:

- In February 2019, India and Norway entered into a collaboration aimed at combating marine pollution. This agreement was part of a broader initiative to strengthen bilateral ties and address pressing environmental issues.

- Option 1: Denmark - Denmark is known for its strong environmental policies, but it did not sign a marine pollution agreement with India in 2019.

- Option 2: Bhutan - While India has a close relationship with Bhutan, marine pollution is not a primary concern in their bilateral discussions, as Bhutan is landlocked.

- Option 3: Norway - India signed a letter of intent with Norway to fight marine pollution. Norway is highly active in addressing ocean health issues.

- Option 4: Cambodia - Cambodia and India's relations focus more on economic and cultural exchanges, not specifically marine pollution.