Explanation:

- Green Revolution: This was a period marked by the introduction of high-yield crop varieties, better irrigation methods, and the use of pesticides and fertilizers, leading to a significant increase in food grain production. It took place during the 1960s and 1970s in Pakistan, as well as other parts of the world.

- Correct Answer

- Five Year Plan: These are centralized economic plans used by a government to develop various sectors, including agriculture. Although they can support agricultural improvements, they aren't the specific event associated with the rapid rise in food grain production.

- Mixed Economy: This is an economic system that incorporates elements of both capitalism and socialism. While it affects agriculture, it doesn't specifically lead to increased food grain production.

- Communes: These are collective farming systems commonly associated with socialist countries. They are not relevant to Pakistan's agricultural improvements.