Which term defines a well-tested, scientifically supported statement that explains how something works?

The correct term is - theory.

Explanation:

A theory is a well tested, scientifically proven and supported over a period of time repeatedly that we'll substantially explain how any natural phenomenon or something work.

The theory is a well-tested explanation whereas the hypothesis is presumption based on prior knowledge of experiments.

Thus, the correct term is - theory.

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.

"d.) carbon dioxide and hydrogen sulfide"