Explanation:

- Option 1: Iraq

- Iraq has been one of the largest suppliers of crude oil to India.

- In December 2019, Iraq was indeed the largest crude oil supplier to India.

- Correct Answer: Iraq

- Option 2: Saudi Arabia

- Historically a major player in the oil market globally.

- Often competes closely with Iraq for the top supplier position to India.

- Option 3: United Arab Emirates

- Important energy partner with India.

- Generally ranked lower compared to Iraq and Saudi Arabia.

- Option 4: Iran

- Has been a significant supplier in the past.

- Supply affected by international sanctions during that period.