The correct answer is: a) Col. Johnstone.
Col. Johnstone was a British officer who served in the Indian Army. He was stationed in Manipur in the 1850s, and it was during this time that he learned about the Manipuri game of polo. He was so impressed by the game that he introduced it to the British, and it soon became a popular sport in England.
Govind Singh was a Manipuri prince who ruled the kingdom from 1798 to 1834. He was a skilled polo player, and he is said to have introduced the game to the British. However, there is no evidence to support this claim.
Bir Tikendrajit was a Manipuri prince who led a rebellion against the British in 1891. He was a skilled polo player, and he is said to have played polo with the British officers who were stationed in Manipur. However, there is no evidence to suggest that he introduced the game to them.
Okram Kumarjit is a modern-day Manipuri polo player. He is a member of the Indian national team, and he has won several international tournaments. He is a very skilled player, but he is not the person who introduced the game to the British.
In conclusion, the Manipuri polo player believed to have introduced the modern game to the British was Col. Johnstone.