**Core Concept**
Folic acid is a B-complex vitamin that plays a crucial role in DNA synthesis, repair, and methylation. It is essential for the proper functioning of the nervous system and the formation of red blood cells.

**Why the Correct Answer is Right**
Folic acid works by being converted into tetrahydrofolate (THF), which serves as a coenzyme for several enzymatic reactions. One such reaction involves the conversion of homocysteine to methionine, which is a vital step in the synthesis of purines and pyrimidines. Folic acid deficiency can lead to an increase in homocysteine levels, which is associated with an increased risk of cardiovascular disease. Folic acid is also essential for the proper functioning of the nervous system, and its deficiency can cause neurological symptoms such as weakness, fatigue, and mental depression.

**Why Each Wrong Option is Incorrect**
**Option A:** Folic acid is involved in the synthesis of nucleic acids, including DNA and RNA. This statement is true.
**Option B:** Folic acid is important for the proper functioning of the nervous system. This statement is true.
**Option C:** Folic acid is not involved in the regulation of blood pressure. This statement is true, and it is the correct answer.

**Clinical Pearl / High-Yield Fact**
Folic acid deficiency can cause megaloblastic anemia, which is characterized by the production of abnormally large red blood cells that are unable to function properly.

**Correct Answer: C. Folic acid is not involved in the regulation of blood pressure.**