The crust is not magnetic near the ocean ridges
In making an experiment their are two types of variable that should be consider, one is the dependent variable and the other one is the independent variables. I the question that dependent variable would be the result or the effect of the gender of mice and the independent is the ways in determining it. So the variables should be fair if you want your result to have no bias. Thus the answer would be letter B. because it has the same variables but different in gender
Sexual Reproductions (i.e. Meiosis)
In Meiosis you have a crossing over stage in prophase I, which will result in the exchange of genetic material + the random assortment at metaphase 1 and 2 increases the variety.
There is approximately 10 billion different ways that a child can look from a mixture of the paternal and maternal genes due to all the random events that happen in meiosis/ sexual reproduction.