Alert - correct answer should be United Arab Emirates.
Option 1 is incorrect. Zayed bin Sultan al-Nahyan was not the President of Oman, that position is traditionally held by the Sultan of Oman.
Option 2 is also incorrect. Kuwait is a constitutional emirate, its head of state is the Emir, not a President, and Zayed bin Sultan al-Nahyan never held that position.
Option 3 is correct. Zayed bin Sultan al-Nahyan was the long-serving President of the United Arab Emirates. He was the principal driving force behind the formation of the UAE, and he served as President from its formation in 1971 until his death in 2004.
Option 4 is incorrect. Saudi Arabia is a monarchy ruled by a king, not a President. Zayed bin Sultan al-Nahyan never ruled Saudi Arabia.