Aresearcher is interested in the eventual divorce rates of people who live together before they get married compared to those who never cohabitate before marriage. the researcher is particularly interested in the couples who cohabitate to see if that leads to higher divorce rates. in a sense, the couples who do not cohabitate are serving as the group.

Experimental group.

Explanation:

In a scientific experiment, there's often two groups: a control group and an experimental group. These two groups are the same, except that for the experimental group, an independent variable is changed. The idea behind this is that a change in the independent variable will yield a different result for the dependent variable. For this experiment, the independent variable is whether couples cohabitate before marriage or not, and the dependent variable is the divorce rate. The group of couples who do not cohabitate will be the experimental group, as the cohabitation variable is changed for this group.

"choosing is refusing" means individuals face an opportunity cost with each decision they make. economists state that every decision involves trade-offs. opportunity cost is the least desirable alternative given up as a result of a decision.