Answer:
a. surveys
Explanation:
Survey research is conducted by distributing questionnaires to a large population and then analyzing the responses of the participants with a the help of a computer based statistical software. With the advent of technology, often these questionnaires are distributed through internet and email and therefore the process becomes very simple for the researchers. Here, the example of psychologists is give who can study many thousands of people at a time through survey research and surely this is one advantage of surveys.
