There Are Measures of Mice Personality Characteristics

There are measures of mice personality characteristics. You can even purchase large numbers of mice that are genetically identical at conception in the form of cloned mice. You have been asked to design a study that looks at the contribution of genetics to anxiety in mice. Which design would best serve your goal?

A) Random mice, raised in identical conditions
B) Two groups of cloned mice raised in identical conditions
C) Two groups of cloned mice each raised under different conditions
D) Four groups of mice - two random, two cloned - each raised under different conditions.