Correct option is B
The correct answer is Option 2: Both (A) and (R) are correct but (R) is not the correct explanation of (A).
Assertion (A) is correct because an experiment involves the manipulation of one or more variables to observe their effect on dependent variables.
Reason (R) is also correct since experimental research design involves the manipulation of variables to identify causal relationships.
However, (R) is not the correct explanation of (A) because experimental research design is a broader concept, whereas an experiment is a specific method within research. (R) defines experimental research design, but it does not directly explain the concept of an experiment as stated in (A).