Collecting data in order to determine whether and to what degree, a relationship exists between two or more quantifiable variables, this is research?

Collecting data in order to determine whether and to what degree, a relationship exists between two or more quantifiable variables, this is research?
(a) Action
(b) Historical
(c) Descriptive
(d) Correlation
✅ Answer: (d) Correlation
Explanation: Correlation research examines relationships between quantifiable variables.