In a linear regression problem, we are using R-squared to measure goodness-of-fit. We add a feature in linear regression model and retrain the same model.Which of the following option is true?

• A. a. if r squared increases, this variable is significant.
• B. b. if r squared decreases, this variable is not significant.
• C. c. individually r squared cannot tell about variable importance. we cant say anything about it right now.
• D. d. none of these.