The International Atomic Energy Agency (IAEA) was established in:

The correct option is 1957.

Step-by-step Explanation:
The International Atomic Energy Agency (IAEA) is an international organization that seeks to promote the peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons.
The genesis of the IAEA was U.S. President Dwight D. Eisenhower's "Atoms for Peace" address to the General Assembly of the United Nations on December 8, 1953.
Following this proposal, the Statute of the IAEA was approved by a conference at the United Nations Headquarters on October 23, 1956, and officially came into force on July 29, 1957.
Therefore, the IAEA was officially established in the year 1957.