**Core Concept**
Hemophilia A is a genetic disorder caused by a deficiency of a specific clotting factor in the blood. This condition is characterized by the inability of blood to clot properly, leading to prolonged bleeding. The underlying principle involves the coagulation cascade and the role of clotting factors.

**Why the Correct Answer is Right**
The correct answer is related to the deficiency of **Factor VIII**, a crucial protein in the intrinsic pathway of blood coagulation. Factor VIII is essential for the activation of Factor X by Factor IXa, which ultimately leads to the formation of a blood clot. A deficiency in Factor VIII impairs this process, resulting in the bleeding manifestations seen in Hemophilia A.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct clotting factor deficient in Hemophilia A.
**Option B:** This option is incorrect because it does not relate to the specific clotting factor involved in Hemophilia A.
**Option C:** This option is incorrect because it is not the correct answer, although it might be related to another condition.
**Option D:** This option is incorrect because it does not specify the correct clotting factor deficient in Hemophilia A.

**Clinical Pearl / High-Yield Fact**
Hemophilia A, also known as classic hemophilia, is the most common type of hemophilia and is caused by a deficiency in **Factor VIII**. This condition predominantly affects males due to its X-linked recessive inheritance pattern.

**Correct Answer:** B. Factor VIII