How should a researcher select subjects for a study in order to generate results that are generalizable

A)  Subjects should all be chosen from the same geographical area and socio-economic class. 
B)  Subjects should be allowed to choose which group they would like to be in. 
C)  Subjects should be from WEIRD societies. 
D)  Subjects should be carefully chosen so that they are a representative sample of the population.

In order to generate results that are generalizable, subjects should be carefully chosen so that they are a representative sample of the population. This means that subjects should be chosen from a variety of geographical areas and socio-economic classes to ensure a diverse sample. Additionally, the sample should be large enough to provide statistically significant results. Avoiding selecting subjects based on their ability to choose a group or selecting subjects from the same population can result in non-generalizable results. Similarly, selecting subjects from a WEIRD (Western, Educated, Industrialized, Rich, and Democratic) society can result in non-generalizable results as the sample may not represent the population as a whole.