Answer:
Systematically describe; assess relations between variable. Option A
Step-by-step explanation:
First, we will fill in the gap in the question, check below;
''Whereas observational research is designed to SYSTEMATICALLY DESCRIBE behavior, correlational research is designed to ASSESS RELATIONS BETWEEN VARIABLE''.
In order to analyze a particular subject there is a part of research techniques to be used in which the analyst just have to observe, the research method or technique for that is called the Observational research. The person observing or the analyst can also be a participant that is part of the subject and still observe.
When you take two things -- variables and you compare and contrast them, you are already using the Correlation research method.