**Core Concept**
Hookworms are parasitic nematodes that infect humans and other animals, causing significant morbidity and mortality worldwide. They thrive in the small intestine, where they attach to the mucosa and feed on blood.

**Why the Correct Answer is Right**
The hookworm's feeding mechanism involves the use of a unique enzyme called aspartic protease, which breaks down hemoglobin into its constituent amino acids. This process allows the hookworm to absorb the essential nutrients necessary for its survival and growth. The hookworms' attachment to the intestinal mucosa also leads to the formation of a blood-filled cavity, which serves as a source of nutrition.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because hookworms do not thrive on carbohydrates, which are not a primary source of nutrition for these parasites.
**Option B:** This option is incorrect because hookworms do not thrive on proteins alone, as they require a source of iron and other essential nutrients that are present in blood.
**Option C:** This option is incorrect because hookworms do not thrive on bile salts, which are actually toxic to these parasites and can lead to their expulsion from the intestine.

**Clinical Pearl / High-Yield Fact**
Hookworm infections are a significant public health concern, particularly in tropical and subtropical regions where sanitation and hygiene are poor. The use of anthelmintic medications, such as mebendazole and albendazole, is effective in treating hookworm infections and preventing their spread.

**Correct Answer: B. Blood**