The correct answer is D. Sampling.
Sampling is a data collection method that involves selecting a subset of individuals from a larger population and collecting data from them. This is done in order to save time and money, as it is often not feasible to collect data from the entire population.
There are a number of different sampling methods, including simple random sampling, stratified sampling, and cluster sampling. The choice of sampling method will depend on a number of factors, such as the size of the population, the desired level of precision, and the cost of collecting data.
Sampling can be a very effective way to collect data, but it is important to be aware of the potential biases that can occur. For example, if the sample is not representative of the population, the results of the study may not be accurate.
Experiments are a data collection method that involves manipulating one or more variables and observing the effect on another variable. This is done in order to determine whether there is a cause-and-effect relationship between the variables.
Observational studies are a data collection method that involves observing a group of individuals without intervening in their lives. This is done in order to describe the characteristics of the group and to identify any relationships between variables.
Surveys are a data collection method that involves asking a group of individuals questions about their beliefs, attitudes, or behaviors. This is done in order to collect data from a large number of people in a relatively short amount of time.