The correlation coefficient, $r = 0.91$, is very close to 1, indicating a strong positive linear association between the two variables $X$ and $Y$. A correlation coefficient of 1 would represent a perfect positive linear relationship, while 0 would indicate no linear relationship, and -1 would represent a perfect negative linear relationship.

Since $r$ is positive and close to 1, the correct interpretation is:

D. There is a strong positive linear association between the two variables.

Would you like further details or clarifications on this? Here are 5 related questions you could explore:

1. How is the correlation coefficient $r$ calculated?
2. What does a negative correlation coefficient mean in practical terms?
3. How can outliers affect the value of $r$?
4. What is the difference between correlation and causation?
5. What is the interpretation of an $r$ value close to 0?

Tip: Always check the sign and magnitude of the correlation coefficient. Positive values indicate a direct relationship, while negative values indicate an inverse one.