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