How many different disciplines had to come together before the full understanding of the theory of plate tectonics could be realized?

Six disciplines, they are:  Paleomagnetics, Seismology, Oceanography, Structural geology, Geography and Paleontology.

Explanation:

Tectonic plates are large blocks that form part of the outer solid layer of planet Earth, responsible for supporting oceans and continents. As the Earth's magma moves within it, the main plates push the others, which change a few millimeters and modify parts of the Earth in parts. They are located in the Earth's layer called the lithosphere.

We know this today, thanks to the discovery that made these plates known. This discovery, along with all theories about how these plates form, move, and influence our planet, was realized thanks to the efforts and amalgamation of six different disciplines. These disciplines are:  "Paleomagnetics, Seismology, Oceanography, Structural geology, Geography and Paleontology".

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.