**Core Concept**
Stratified sampling is a type of probability sampling method used in research to ensure that the sample accurately represents the population. It involves dividing the population into distinct subgroups or strata, based on relevant characteristics, and then randomly sampling from each subgroup.

**Why the Correct Answer is Right**
Stratified sampling is ideal when the population has distinct subgroups with different characteristics, and the researcher wants to ensure that the sample is representative of each subgroup. This method is particularly useful when the population is heterogeneous, and the researcher wants to examine the relationships between variables within each subgroup. Stratified sampling allows researchers to maintain the internal validity of their study by ensuring that the sample is representative of the population, which is essential for making generalizations about the population.

**Why Each Wrong Option is Incorrect**
**Option A:** Cluster sampling is a type of probability sampling method where the population is divided into clusters, and then random samples of clusters are selected. This method is not ideal for populations with distinct subgroups, as it may lead to biased samples.
**Option B:** Systematic sampling involves selecting samples based on a fixed interval or system, such as every 10th item. This method is not suitable for populations with distinct subgroups, as it may not account for the differences between subgroups.
**Option C:** Convenience sampling involves selecting samples based on ease of access or convenience. This method is not ideal for populations with distinct subgroups, as it may lead to biased samples and lack generalizability.

**Clinical Pearl / High-Yield Fact**
Stratified sampling is a crucial technique in research to ensure that the sample accurately represents the population, which is essential for making generalizations about the population.

**Correct Answer: D. This answer is not provided, but Stratified sampling is ideal for populations with distinct subgroups.