Explanation:

• The Collective Security Treaty was signed by Armenia, Kazakhstan, Kyrgyzstan, Russia, Tajikistan, and Uzbekistan on May 15, 1992. Current CSTO members are Armenia, Belarus, Kazakhstan, Kyrgyzstan, the Russian Federation and Tajikistan.
• It is a Russia-led military alliance of seven former Soviet states that was created in 2002. The CSTO’s purpose is to ensure the collective defence of any member that faces external aggression. It is described by political scientists as the Eurasian counterpart of NATO.
• Hence option 2nd is correct.