You are adding more features to a linear regression model and hope they will improve your model. If you add an important feature, the model may result in. 1. Increase in R-square
2. Decrease in R-square
A) Only 1 is correct
B) Only 2 is correct
C) Either 1 or 2
D) None of these

The answer is "Option A".

Explanation:

Add extra functionality, otherwise, it increases the R-square value, which is defined in the following points:      

To incorporate essential elements, R-square is explicitly promoted. It Increases the R-square value, which is an additional feature. It removes the features, which provide the value of the reduce R-square. After incorporating the additional features is used as the model, which is R-square, which is never reduced.

2is the answer trust me