The correct answer is: B. Experiments
An experiment is a research method that involves manipulating one or more variables to observe their effects on other variables. The manipulated variable is called the independent variable, and the variables that are observed are called the dependent variables. Experiments are often used to test cause-and-effect relationships.
Observational studies are a type of research method in which the researcher observes participants without interfering with their behavior. Observational studies can be used to describe the prevalence of a condition or behavior, or to identify factors that are associated with a condition or behavior. However, observational studies cannot be used to determine cause-and-effect relationships.
Surveys are a type of research method in which the researcher asks participants questions about their attitudes, beliefs, or behaviors. Surveys can be used to collect data from a large number of people, but they can be limited by the accuracy of the participants’ responses.
Interviews are a type of research method in which the researcher asks participants questions in a face-to-face or phone conversation. Interviews can be used to collect in-depth data from a small number of people, but they can be time-consuming and expensive.