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 view on midlife?

A) Unlike Valliant,according to Levinson,only males experience midlife crisis.
B) Unlike Levinson,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) Unlike Levinson,Valliant's study was mainly focused on white,middle-aged,male population within the upper SES of society.