According to Willerman (1979),a Problem with Attempting to Study the Effects

According to Willerman (1979) ,a problem with attempting to study the effects of nonshared environments is that:

A) there are so many environmental variables that exert an impact on personality that each variable alone might account only for a tiny fraction of the variance.
B) the nonshared environmental effects on each child in a family are too subtle to analyze using current methods.
C) the effects of shared family environments interfere with the effects of nonshared family environments.
D) the equal environments assumption is violated by variables attributable to nonshared family environment.