**Core Concept**
Random sampling is a statistical technique where every member of a population has an equal chance of being selected for a study. It's essential in epidemiology and research to ensure that the sample is representative of the population. Random sampling can be used in various forms, including simple random sampling, cluster sampling, and stratified sampling.

**Why the Correct Answer is Right**
Quota sampling, on the other hand, is a non-random sampling technique where the sample is selected based on pre-defined characteristics or quotas. This method does not ensure that every member of the population has an equal chance of being selected, which is a fundamental principle of random sampling. In quota sampling, the researcher selects participants based on certain criteria, such as age, sex, or socioeconomic status, without randomly selecting them from the population.

**Why Each Wrong Option is Incorrect**
**Option A:** Cluster sampling is a type of random sampling where the population is divided into clusters, and a random selection of clusters is made. This ensures that every member of the population has an equal chance of being selected, making it a form of random sampling.
**Option C:** Stratified sampling is a type of random sampling where the population is divided into subgroups or strata, and a random sample is taken from each subgroup. This ensures that every member of the population has an equal chance of being selected, making it a form of random sampling.
**Option D:** Simple random sampling is a type of random sampling where every member of the population has an equal chance of being selected. This is the most basic form of random sampling, where participants are randomly selected from the population without any pre-defined characteristics or quotas.

**Clinical Pearl / High-Yield Fact**
When designing a study, researchers must carefully consider the sampling method to ensure that the sample is representative of the population. Quota sampling can be useful in certain situations, but it's essential to recognize its limitations and potential biases. Always remember that random sampling is essential for ensuring the validity and generalizability of research findings.

**✓ Correct Answer: B. Quota sampling**