Explanation:
The correct option is 'a'. The classic triad of fat embolism syndrome (FES) includes respiratory distress, neurological abnormalities, and a petechial rash, typically occurring 24 to 72 hours after major trauma involving long bone (especially femur) or pelvic fractures. The petechial rash is considered pathognomonic but is only present in 20-50% of cases.

Reference: Gurd AR. Fat embolism: an aid to diagnosis. J Bone Joint Surg Br. 1970;52(4):732-737.