A is the correct answer.
Great Britain, France, the Soviet Union, and the United States were the key allied powers during World War II. They fought primarily against Germany, Italy, and Japan (although the UK and the US did most of the fighting against Japan).
Answer:
This type of research is an example of the research method called cross-sectional research.
Explanation:
Cross-sectional research is a research design or method used in observational studies. The reseracher measures the dependent variable in different population groups at the same point in time. The population groups or cohorts are chosen depending on the research question, they can be based on age (like in the example in the question), gender or race, among other categories. Usually the outcomes are compared to one another.
