Explanation:

Correlation Coefficient (r):
- The correlation coefficient (r) measures the strength and direction of a linear relationship between two variables.
- The value of r ranges from -1 to 1, where:
- r = 1 indicates a perfect positive linear relationship
- r = -1 indicates a perfect negative linear relationship
- r = 0 indicates no linear relationship

Parallel Regression Lines:
- When two regression lines are parallel, it means that the relationship between the variables is consistent across the two groups or conditions being compared.
- This implies that the correlation coefficient (r) between the two variables is the same for both groups.

Relationship between r and Parallel Regression Lines:
- If two regression lines are parallel, it means that the correlation coefficient (r) between the variables is the same for both groups.
- Therefore, the correlation coefficient (r) will be the same for both regression lines, and it will not be affected by the parallelism of the lines.

Conclusion:
- When two regression lines are parallel, the correlation coefficient (r) will remain the same for both lines.
- Therefore, if two regression lines are parallel, the value of r will not change, and it could be any value between -1 and 1 depending on the strength and direction of the linear relationship between the variables.
- So, the correct answer is (3) 1.