Which of the following events was considered the end of the Cold War?

Answer: when the iron curtain (berlin wall) came down is pretty much considered the end

the signing of a mutual nonaggression pact in 1990

Explanation:

The signing of the NFT, nuclear forces treaty, between the US and the USSR eliminated a great arsenal of intermediate and short ranged atomic weapons in the European stage.

It was signed in 1987, which lead to both parts to agree on removing missile bases settled in west and eastern countries in an effort to demilitarize Europe and lessen tensions.

Cooperation between the socialist world and the West began, as in 1993 Chemical Weapons Convention was signed eliminating and banning the manufacturing and use of chemical weapons.

Reagan met Gorbachev, and eventually the former socialist countries gained independence giving most of its warheads to Russian Federation.

For example Ukraine, gave all nuclear arsenal and no longer manufactered.

Many former USSR republics approached the West with US support.