Oliver is determining the number of males in his math class. Oliver is collecting what kind of data? A) bivariate B) categorical C) qualitative D) univariate

When Oliver is considering the number of males, he typically assigns people to two categories: make or female, which makes the variable bi-variate : with two values. ("bi" means "two).

If he's more inclusive, and adds the category of "other", it would be a categorical data - with 3 categories.