Donna, a 33-year-old divorcee with two sons, and mark, a 50-year-old divorcee with two daughters, become engaged and live together. although they are strongly committed to one another, they never actually go ahead with the marriage. this is an example of

The answer is cohabitation.

Explanation:

As the name implies, cohabitation refers to a situation in which a couple lives together despite not being married. This type of relationship is usually long-term.

Recent studies show that cohabitation is becoming the fastest-growing type of lifestyle for couples, in contrast to married life (which is still the most common, but is slowly decreasing).

answer; i believe that the correct answer is (d); // supercontinent

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.