The correct answer is option 4, Prothrombin. Vitamin K plays a key role in the synthesis (production) of prothrombin, which is a protein that is essential for blood clotting. When a blood vessel is damaged, prothrombin is converted into thrombin, which then activates other substances involved in clot formation. This helps to stop bleeding and initiate the healing process.

Let`s examine the other options to further understand why they are not correct:

- Option 1: Albumin is a protein responsible for maintaining osmotic pressure in the blood and transporting various substances, but it is not synthesized by Vitamin K.

- Option 2: Antibodies are proteins produced by the immune system to help fight against infections and foreign substances. They are not synthesized by Vitamin K.

- Option 3: Globulin refers to a group of proteins that are involved in various functions such as transport, immunity, and blood clotting. However, Vitamin K does not play a specific role in their synthesis.

Therefore, the correct answer is option 4, Prothrombin.