A 3-year-old boy with cystic fibrosis is evaluated for the acute onset of an uncontrollable nosebleed. There is no family history of a bleeding disorder. A few large bruises are seen on the legs; no other abnormalities are noted. Prothrombin and partial thromboplastin times are prolonged. The patient's abnormalities are likely to improve with treatment using a cofactor for which process?
A) Carboxylation of prothrombin
B) Conversion of homocysteine to methionine
C) Farnesylation of ras
D) Hydroxylation of procollagen
E) Phosphorylation of pyruvate dehydrogenase