The response that best explains why Ivan IV created the oprichnina during his reign is: Ivan IV was struggling against the boyars and wanted to limit their power.
The oprichnina was a policy implemented by Ivan IV (also known as Ivan the Terrible) to consolidate his power and weaken the influence of the nobility (boyars). It allowed him to create a separate administrative region loyal directly to him, enabling him to control and suppress potential threats from the boyars and other elites in Russian society.