Which of the Following Hypothetical Research Findings Would Present a Problem

Multiple Choice

Which of the following hypothetical research findings would present a problem for researchers trying to interpret results from a twin-study design?

A) Parents of monozygotic twins treat the two twins more alike than do parents of dizygotic twins.
B) Dizygotic twins don't look as much like one another as do monozygotic twins.
C) Parents treat female pairs of twins differently than they treat male twins.
D) There are more dizygotic twins born each year than monozygotic twins.