The main issue addressed by the Kyoto Protocol, which came into force recently, is controlling the emission of greenhouse gases. This global agreement aims to combat climate change by setting binding targets for developed countries to reduce their greenhouse gas emissions.

Option 1, preserving biodiversity and conserving plants and animals, is not the main focus of the Kyoto Protocol. While climate change can have an impact on biodiversity, the primary goal of this agreement is to reduce greenhouse gas emissions.

Option 2, controlling the production of weapons of mass destruction, is not related to the Kyoto Protocol. The focus of the protocol is specifically on addressing climate change and reducing greenhouse gas emissions.

Option 3, promoting a free-trade block consisting of ASEAN members and other East Asian countries, is also unrelated to the Kyoto Protocol. The protocol primarily focuses on environmental concerns rather than economic integration and trade agreements.

Therefore, option 4, controlling the emission of greenhouse gases, is the correct answer as it accurately reflects the main issue that is addressed by the Kyoto Protocol.