The type of causal reasoning involved when explaining a single situation in terms of many possible causes is known as explanation.

idiographic explanation

Explanation:

Type of causal reasoning is an idiographic explanation  

we know that there are 2 types of  approach for understanding the social life

and here idiographic approach use for understanding single or individual type case or event but a nomothetic approach that is used for understanding large scale social pattern

so here also cause of the single situation is exhaustively examined  

so correct answer is an idiographic explanation

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.

in this scenario it would be the consumer demand as most influential in making the decision. the band members need to figure out where and from whom they will make the most money, in other words who out of the two consumer groups - football fans or car drivers - will spend their money, who is more likely to contribute to their cause and buy what they are offering.