A Public Health Researcher Wants to Use Regression to Predict $\quad \mathrm { y } =$

A public health researcher wants to use regression to predict the sun safety knowledge of pre-school children. The researcher randomly sampled 35 preschoolers, assigned them to one of two groups, and then measured the following three variables:
SUNSCORE: $\quad \mathrm { y } =$ Score on sun-safety comprehension test
READING: $\quad \mathrm { x } _ { 1 } =$ Reading comprehension score
GROUP: $\quad \quad x _ { 2 } = 1$ if child received a Be Sun Safe demonstration, 0 if not

A regression model was fit and the following residual plot was observed.
Predicted value of $y$

Which of the following assumptions appears violated based on this plot?

A) The errors are normally distributed
B) The errors are independent
C) The mean of the errors is zero
D) The variance of the errors is constant