Which most distinctive sign of flail chest is assessed by a nurse?

Option C is correct
Paradoxical chest movement is the most distinctive sign of flail chest assessed by a nurse
Flail chest occurs when a segment of the rib cage breaks due to trauma. The broken ribs detach from the rest of the chest wall. This causes difficulty in breath for the patient.

During inhalation the broken part moves inward and the other parts of the chest expand and during exhalation, the broken part expands and the rest of the chest move inwards causing paradoxical movement of the chest.

Paradoxical chest movement-flail chest results from fracture of two or more ribs in at least two places each. this results in a floating section of ribs. because this section is unattached to the rest of the bony rib cage, this segment results in paradoxical chest movement. this means that the force of inspiration pulls the fractured segment inward, while the rest of the chest expands. similarly, during exhalation, the segment balloons outward while the rest of the chest moves inward. this is a telltale sign of flail chest.