Explanation:
The correct option is 'c'. The 'Delta P' concept is crucial for diagnosing acute compartment syndrome. A Delta P (Diastolic Blood Pressure - Compartment Pressure) of less than 30 mmHg indicates critically impaired capillary perfusion and is widely accepted as an absolute indication for emergency fasciotomy, regardless of the absolute compartment pressure reading.

Reference: McQueen MM, Court-Brown CM. Compartment monitoring in tibial fractures. The pressure threshold for decompression. J Bone Joint Surg Br. 1996;78(1):99-104.