Zach's behavior of pushing other children typically occurs on the playground. the playground would be a(n) setting for zach's behavior.

a. analogue
b. manipulated
c. natural
d. controlled

natural

Explanation:

In research, natural setting refers to the place where subjects can freely act without any intervention by the researchers.

If you want to examine how children behave toward another children, playground will be considered as a 'natural settings'. The use of natural settings tend to provide a set of data that are closer to actual truth if compared to a setting that controlled by the researchers.

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.