The following diagram is drawn to study:: (A) Trend of a variable over a period of time, (B) Frequency of occurrence of events, (C) Mean & median values of the given data, (D) Relationship between two given variables
Answer is D. SCATTER DIAGRAM

Also known as ‘Correlation diagram’ or ‘Dot diagram’.
Is used to depict ‘correlation (relationship) between 2 quantitative variables’.
‘Vertical axis in scatter diagram: should be the dependent or the outcome variable.
In a scatter diagram, 2 imaginary lines are drawn along the distribution of dots/scatter.