Most successful parasites are those which do not

Options

A. Grow free
B. Kill their host
C. Reproduce sexually
D. Survive in soil

Answer

**Step-by-Step Solution:**

1. **Understanding the Definition of a Parasite**:
- A parasite is an organism that lives on or in a host organism and gets its food at the expense of its host. The relationship is typically harmful to the host.

2. **Analyzing the Options**:
- **Option 1: Grow Free**: Parasites cannot grow freely as they depend on a host for sustenance.
- **Option 2: Kill Their Host**: Successful parasites do not kill their host because they rely on the host for food and shelter. If the host dies, the parasite loses its source of nourishment.
- **Option 3: Reproduce Sexually**: Many parasites can reproduce sexually, but this is not a defining characteristic of a successful parasite.
- **Option 4: Survive in the Soil**: While some parasites may need to survive in the soil at certain life stages, this is not a requirement for all successful parasites.

3. **Identifying the Correct Answer**:
- The most successful parasites are those that do not kill their host (Option 2). This allows them to continue feeding and reproducing without losing their source of sustenance.

4. **Conclusion**:
- Therefore, the correct answer to the question is that the most successful parasites are those which do not kill their host.

---