Final answer:
Option d, as the value of x increases, the value of the error term also increases, is a violation of one of the major assumptions of the simple regression model. Option d.
Step-by-step explanation:
The violation of one of the major assumptions of the simple regression model is option d. As the value of x increases, the value of the error term also increases.
In a simple regression model, it is assumed that the error terms are independent of each other (option a), the error terms show no pattern (option b), and a histogram of the residuals forms a bell-shaped, symmetrical curve (option c).
When the value of x increases and the value of the error term also increases, it means there is a systematic relationship between x and the error term, violating the assumption of independence.
Option d.