The decision in a multiply-injured patient with chest trauma and four long-bone fractures depends on physiological status. The stem states resuscitation has succeeded and the patient is haemodynamically stable, so we are choosing definitive rather than temporary fixation.
Guiding principles:
$1.$ For an unstable patient, perform damage-control external fixation of all long bones - quick, low-stress, life-saving.
$2.$ For a stabilized patient, proceed to the best long-term implant per bone.
Applying principle $2$ here:
$\bullet$ Femur: closed intramedullary nail - the recognised gold-standard definitive treatment of diaphyseal femoral fractures, enabling early rehabilitation.
$\bullet$ Tibia: external fixation provides a safe, low-burden definitive option given the systemic and soft-tissue insult already sustained.
Reversing the constructs (option 2), choosing the fastest technique (option 3, a DCO concept for the unstable), or externally fixing everything definitively (option 4) are all inferior here.
\[\boxed{\text{Nail the femurs; external fixation of the tibiae}}\]