**Core Concept**
The half-life of prothrombin is a critical parameter in coagulation medicine, representing the time required for the concentration of prothrombin to decrease by half in the bloodstream. Prothrombin, also known as factor II, plays a pivotal role in the coagulation cascade, converting fibrinogen to fibrin to form a blood clot.

**Why the Correct Answer is Right**
The half-life of prothrombin is approximately 60 hours in healthy individuals, which is relatively long compared to other clotting factors. This is due to the slow turnover rate of prothrombin, which is synthesized in the liver and regulated by the vitamin K-dependent carboxylase enzyme. The half-life of prothrombin is an essential factor in the management of patients on anticoagulant therapy, particularly warfarin, which inhibits vitamin K-dependent carboxylase and prolongs prothrombin time.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the half-life of prothrombin is not 24 hours. While some clotting factors have shorter half-lives, prothrombin's prolonged half-life is a characteristic feature of its coagulation pathway.
**Option B:** This option is incorrect because the half-life of prothrombin is not 12 hours. This value is more representative of the half-life of factor VII, another vitamin K-dependent clotting factor.
**Option C:** This option is incorrect because the half-life of prothrombin is not 90 hours. This value is slightly longer than the actual half-life, but it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
When managing patients on warfarin, it is essential to consider the half-life of prothrombin, as it affects the timing of therapeutic anticoagulation and the risk of bleeding complications. Monitoring prothrombin time and adjusting warfarin dosages accordingly can help minimize these risks.

**Correct Answer:** C. 60 hours.