The correct option is C. scolex. Explanation of the Correct Answer The scolex is the head of a tapeworm, which is a type of parasitic flatworm belonging to the class Cestoda. The scolex is a specialized structure that allows the tapeworm to attach itself to the intestinal wall of its host, which is typically a vertebrate, including humans. Structure and Function of the Scolex:

1. Attachment Mechanism: The scolex is equipped with various structures that facilitate attachment. These can include:
2. Suckers: These are cup-like structures that help the tapeworm cling to the host's intestinal lining.
3. Hooks: Some species of tapeworms have hooks on their scolex that further enhance their ability to anchor themselves securely.
4. Nutrient Absorption: By attaching firmly to the host, the tapeworm can absorb nutrients directly from the host's digested food through its skin, as it lacks a digestive system of its own.
5. Reproductive Role: The scolex is also important for the tapeworm's reproductive strategy, as it allows the organism to remain in a stable position within the host, maximizing its chances of reproduction.

Why the Other Options are Incorrect

• A. Sucker: While the term "sucker" refers to a part of the scolex, it is not the correct term for the entire head of the tapeworm. The scolex encompasses the suckers and other structures, making "scolex" the more accurate term.
• B. Rostellum: The rostellum is a specific part of the scolex in some tapeworms. It is a protruding structure that may bear hooks or other features. However, it is not synonymous with the entire head of the tapeworm, which is why this option is incorrect.
• D. Hook: Similar to the rostellum, hooks are structures found on the scolex of some tapeworms that aid in attachment. However, "hook" refers to a specific feature rather than the entire head structure, making this option incorrect as well.

Summary of Key Points

• The scolex is the head of the tapeworm, crucial for attachment and nutrient absorption.
• It contains suckers and, in some species, hooks that enhance its ability to cling to the host.
• The terms "sucker," "rostellum," and "hook" refer to specific parts or features of the scolex, not the entire head.

Revision Summary

• The head of a tapeworm is called the scolex.
• The scolex has structures like suckers and hooks for attachment.
• The rostellum is a specific part of the scolex, not the whole head.
• Understanding the scolex is essential for grasping how tapeworms survive and reproduce in their hosts.