For which method might a researcher employ a number of techniques such as interviews,direct observations,and psychological testing

A)  a survey
B)  naturalistic observation 
C)  a correlation
D)  a case study

Psychological Testing

Psychological testing involves the use of standardized tests to evaluate an individual's cognitive, emotional, and psychological functioning.

Interviews

A method of gathering information by asking questions orally, used in various contexts including research, journalism, and employment.

Direct Observations

A research method where behaviors or events are watched and recorded as they naturally occur, without interference or manipulation by the observer.