please help me with this

Problem 3. [3 marks] The simple linear regression model y = Bo + Bix + & is fitted to Dataset A and Dataset B, respectively, and the resulting residual plots of e; vs fitted value yi are given above. (3a) [2 marks] It is known that only one of the datasets allows test on the lack-of-fit of the simple linear regression model. Which dataset is it? Briefly explain. (3b) [1 mark] Suppose the lack-of-fit test for the dataset in (3a) is significant (say, p-value