Why are these two bills lettered differently at the beginning? The letters are chosen by the elected official that introduced the bill

The letters are randomly chosen by the Secretary of State

The letters alternate between HB and SB

The letters refer to the house in which the bill originated

The letters are randomly chosen by the Secretary of State

the answer is

a) revise existing treaties

b) do away with political alliances

c) prevent the spread of communism

d) bring an end to european colonization

the main goal of the southeast asia treaty organization was to prevent the spread of communism in southeast asia.