Answer:
C) Platelets
Explanation:
Hemophilia is caused by a lack of clotting factors. Because platelets (or lack thereof) are what is responsible for how the blood clots, it can be reasonably inferred that the answer is C.
(Platelets secrete procoagualants, which are clotting factors. If there is a genetic issue with how these clotting factors work, then the platelets will not be useful.)
