The universal donor of RBCs, but not necessarily plasma, is blood type.

A. Thromboplastin: Thromboplastin (tissue factor) initiates the extrinsic coagulation cascade and promotes clot formation; injecting it would increase clotting, not prevent heart attack or stroke.
B. Fibrinogen: Fibrinogen is the soluble precursor that is converted to fibrin during clot formation; giving fibrinogen would support clot formation, not reduce it.
C. Fibrin: Fibrin is the insoluble protein that forms the mesh of a clot; injecting fibrin would directly contribute to clotting.
D. Factor X: Factor X is a key coagulation factor (when activated to Xa it drives thrombin formation); administering it would promote coagulation rather than prevent it.
E. Heparin: Heparin is an anticoagulant that enhances antithrombin activity and reduces clot formation; it is used to prevent or treat thrombosis and reduce risk of heart attack/stroke.

A. Insulin: insulin is a low-concentration peptide hormone (produced by pancreas), not the major plasma protein.
B. Bilirubin: bilirubin is a breakdown product of heme (not a protein) and is present in low concentrations.
C. Albumin: albumin is the most abundant plasma protein (produced by the liver); it maintains oncotic pressure and binds/ transports many substances.
D. Creatinine: creatinine is a small waste molecule (not a protein) present at low concentration.
E. Creatine: creatine is a small molecule involved in muscle energy storage, not a plasma protein.