Final answer:
The correct term for a group of randomly selected subjects that matches the population on key traits like age and sex is a 'representative sample'. It is used because it gives all members of the population an equal chance to be included in the study, which helps to generalize findings.
Step-by-step explanation:
A group of randomly selected subjects for a study that matches the population on important characteristics such as age and sex is called a representative sample. The correct answer to the question is B) a representative sample. This is because a representative sample is a subset of the population that has the same characteristics as the population, ensuring that the findings can be generalized to the entire population.
Choosing a random sample is indeed an effective way to select participants because d. Everyone has the same chance of being part of the study, which mitigates selection bias and ensures that every member of the population has an equal likelihood of being chosen, thus the findings can be more readily generalized to the broader population.