Someone said b and someone else said E please help ASAP and true to be sure about answer

Consider a linear regression model with just one independent variable. Of the following statements, which of them is a good reason for looking at a residual plot? 1. To see if we should consider a higher-order polynomial model 2. To see if the error variance is constant 3. To see if there are any suspicious outliers Use "Formula Sheet Fall 2020" if necessary. Select one: O a. Only 1 O b. Only 2 O c. Only 3 O d. Only 2 and 3 O e. 1 and 2 and 3