When designing the technical solution for a disaster recovery site, the PRIMARY factor that should be taken into consideration is the:

Recovery window.

Explanation:

Disaster recovery can be defined as a field in security planning that comprises of policies and procedures aimed at protecting a business firm from the effects of any significant negative event.

This ultimately implies that, having an effective disaster recovery strategy or plan in place would help a business firm to quickly resume normal operations or maintain its mission-critical functions in the event of any disaster (disruption).

Hence, when designing the technical solution for a disaster recovery site, the primary factor that should be taken into consideration is the recovery window. A recovery window is typically the time frame between the occurrence of a disaster and the restoration of essential operations. This time frame is mainly defined by the executive board or management of a business firm.

c is the correct answer.