1. Association of South-East Asian Nations (ASEAN) (A): ASEAN is a regional intergovernmental organization that comprises ten Southeast Asian countries. These member states include Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam. ASEAN was established with the primary goal of promoting economic cooperation, regional peace, and stability.

2. European Union (EU) (B): The European Union is a political and economic union of 27 European countries. It was created to foster economic integration, facilitate trade, and promote peace and cooperation in Europe. The EU has its own single market, a common currency (the Euro, used by 19 of its members), and a customs union. 

3. South Asian Free Trade Agreement (SAFTA) (C): SAFTA is a regional trade agreement among the South Asian Association for Regional Cooperation (SAARC) member states. The SAARC member countries include Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka. SAFTA aims to promote trade and economic cooperation within the South Asian region by reducing or eliminating tariffs on intra-regional trade. 

4. The United Nations Organisation (UNO) (D) is not a regional trade block; it is an international organization that focuses on global issues such as peace and security, development, human rights, and international cooperation. While it may play a role in facilitating trade and development initiatives, it is not a regional trade block itself.