A successful search requires that victims be _____ and then _____.

In the context of a successful search during structural collapse rescue operations, the correct sequence is to first "detect" victims. This refers to the initial stage of identifying signs of potential victims, which could include sounds, movement, or even visual cues through debris. After detection, the next critical step is to "locate" them precisely within the structure. This involves pinpointing their exact position, which is essential for planning the extraction and ensuring the safety of both the rescuers and the victims.

While other options suggest important concepts related to rescue operations, they do not capture the specific flow of actions required in a search and rescue scenario. For instance, identifying and extracting implies a more definitive awareness of the victim's status without accommodating the nuances of initial detection and precise location determination. Marking and rescuing, as well as finding and retrieving, do not accurately reflect the critical preconditions—detection followed by precise location—that are necessary for maneuvering effectively through a collapsed structure. Thus, the emphasis on detection and location aligns with standard operational procedures in structural collapse rescue, making it vital for achieving a successful outcome.