Which of the following incidents happened in 1997?

The Kyoto Protocol was signed

The correct answer is Option 1 - The Kyoto Protocol was signed

Option 1: The Kyoto Protocol was signed - 1997
Option 2: Attack on America by Al-Qaeda - 2001
Option 3: The Non-Proliferation Treaty was signed - 1968
Option 4: CTBT was signed - 1996

On December 11, 1997, delegates from more than 150 countries signed the Kyoto Protocol, an agreement to lower the number of greenhouse gases released into the atmosphere.