Flukes and tapeworms:

Options

A. show cephalization
B. have well-developed reproductive systems
C. have well-developed nervous systems
D. are plant parasites

Explanation

### Step-by-Step Solution:

1. **Identify the Organisms**: Flukes and tapeworms are both types of parasitic worms known as helminths. They are not free-living organisms; instead, they rely on a host for survival.

2. **Understand Their Structure**:
- Flukes have a leaf-like, flattened body shape.
- Tapeworms have an elongated, flat body structure.
- Both lack a cylindrical shape, which is characteristic of roundworms.

3. **Determine Their Habitat**:
- Flukes typically infect the circulatory system and liver of their hosts.
- Tapeworms primarily inhabit the digestive system of their hosts.

4. **Identify Their Hosts**:
- Both flukes and tapeworms usually infect vertebrates, including humans.

5. **Examine Cephalization**:
- Cephalization refers to the development of a head region with a concentration of sensory organs and a nervous system.
- Flukes and tapeworms lack cephalization, indicating that they do not have a well-defined head or complex nervous system.

6. **Assess the Nervous System**:
- The nervous system of flukes and tapeworms is not well developed. It consists of a simple network of nerves rather than a complex structure.

7. **Evaluate the Reproductive System**:
- Both flukes and tapeworms have a well-developed reproductive system. They can produce both male and female gametes, either within the same organism (hermaphroditic) or in separate organisms.

8. **Consider the Nature of Their Parasitism**:
- Flukes and tapeworms are animal parasites, not plant parasites.

9. **Summarize Findings**:
- They do not exhibit cephalization.
- They have a well-developed reproductive system.
- They do not have a well-developed nervous system.
- They are animal parasites, not plant parasites.

10. **Conclusion**: The correct answer to the question is that flukes and tapeworms have a well-developed reproductive system.