Explanation:

- Correct Answer: Option 3 - Shandur

- Shandur is home to the world's highest polo ground, located at an elevation of approximately 3,700 meters (12,139 feet) in the Gilgit-Baltistan region of Pakistan.

- The Shandur Polo Festival, held annually in July, attracts many tourists and showcases a traditional free-style version of polo.

- Option 1: Kasur

- Kasur is a city in the Punjab province of Pakistan and is not known for a polo ground.

- It is primarily known for its historical sites and being the birthplace of the famous Sufi poet Bulleh Shah.

- Option 2: Attock

- Attock is a city in the Punjab province of Pakistan, known for its strategic location near the confluence of the Indus and Kabul rivers.

- It does not have a notable polo ground.

- Option 4: Okara

- Okara is also located in Punjab and is renowned for agriculture and dairy production.

- It does not host the world’s highest polo ground.