The head region of a tapeworm is called the :

Options

A. proglottid
B. cercaria
C. sporocyst
D. scolex

Explanation

**Step-by-Step Solution:**

1. **Understanding Tapeworm Structure**: Tapeworms are parasitic worms that belong to the phylum Platyhelminthes. They have a distinct body structure that includes several parts.

2. **Identifying the Head Region**: The head region of a tapeworm is specifically known as the "scolex." This is the part that attaches to the host's intestinal wall.

3. **Recognizing Other Parts**: The tapeworm also has a neck and a long body made up of segments called proglottids. The proglottids are not part of the head but are found in the strobila, which is the main body of the tapeworm.

4. **Evaluating the Options**:
- **Proglottid**: Incorrect, as this refers to the segments of the body, not the head.
- **Sarcaria**: Incorrect, as this is a larval stage of certain parasitic worms, not related to the head of a tapeworm.
- **Sporocyst**: Incorrect, as this term refers to a developmental stage in the life cycle of some parasites, not the head of a tapeworm.
- **Scolax**: Correct, as this is the term for the head region of a tapeworm.

5. **Conclusion**: The correct answer to the question "The head region of a tapeworm is called the:" is "scolex."