Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks.

The Association of Southeast Asian Nations (ASEAN) is an organization of ten Southeast Asian countries: Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, (19) _________ Philippines, Singapore, Thailand and Vietnam. It promotes political, economic, cultural and social cooperation (20) _________ its members. Although ASEAN works for peace and stability in Southeast Asia, it is not a defence organization.

The members of ASEAN cooperate in such fields (21) ________ population control, prevention of drug abuse, (22) ________ research and combating terrorism. Teachers, students and artists of the member nations exchange visits. In addition, the organization(23) ________ plans to promote tourism in ASEAN countries and to encourage programs of Southeast Asian studies. It works to reduce trade barriers among the members.

A. the                       

B. a                    

C. an                    

D. Ø