Which of the Following Is a Major Difference Between Levinson's

Which of the following is a major difference between Levinson's and Valliant's views on midlife?

A) Unlike Valliant, Levinson believes that only males experience a midlife crisis.
B) Unlike Levinson, Valliant maintains that only a minority of adults experience a midlife crisis.
C) Levinson maintains that the transition period to midlife is 6 years, while Valliant holds it to be 8 years.
D) Unlike Levinson, Valliant's study was mainly focused on white, middle-aged, male population within the upper SES of society.