The correct answer is Option 2: ASEAN.

The Regional Comprehensive Economic Partnership (RCEP) is a free trade agreement that was signed on November 15, 2020, by 15 Asia-Pacific countries. The agreement is aimed at creating a comprehensive economic partnership in the region and promoting regional economic integration.

The RCEP includes the 10 member states of the Association of Southeast Asian Nations (ASEAN), namely Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam. It also includes five of ASEAN`s Free Trade Agreement partners: China, Japan, South Korea, Australia, and New Zealand.

While the G20, SCO, and SAARC are also groups of countries that have made efforts towards economic cooperation and integration, they are not directly involved in the RCEP.

The G20, or Group of Twenty, is a forum for the world`s 20 largest economies to discuss economic and financial issues. It includes countries such as the United States, China, Japan, and Germany, but does not include many Southeast Asian countries.

The SCO, or Shanghai Cooperation Organization, is a political, economic, and military organization that includes China, Russia, and several Central Asian countries, but not any Southeast Asian countries.

The SAARC, or South Asian Association for Regional Cooperation, is a regional intergovernmental organization that includes Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka, but not any Southeast Asian countries.

In summary, the RCEP is a free trade agreement between 15 countries, including the 10 ASEAN member states and 5 of ASEAN`s Free Trade Agreement partners. Therefore, the correct answer is Option 2: ASEAN.