Correlated characters are those which occur

Options

A. At random
B. In groups or units
C. In a particular portion of body
D. In certain groups of organisms

Answer

**Step-by-Step Solution:**

1. **Understanding Correlated Characters**: Correlated characters are traits or features that tend to occur together in organisms. They are not random but show a pattern or relationship.

2. **Evaluating the Options**:
- **Option 1: At random** - This suggests that correlated characters appear without any specific order or relationship, which is incorrect.
- **Option 2: In groups or units** - While some characters may appear in groups, this does not specifically define correlated characters.
- **Option 3: In a particular portion of the body** - This implies a location-based occurrence, which does not accurately describe correlated characters.
- **Option 4: In certain groups of organisms** - This indicates that correlated characters are specific to certain groups, which aligns with the definition of correlated characters.

3. **Conclusion**: Based on the evaluation, correlated characters are traits that occur in certain groups of organisms, which helps in classifying and grouping them into categories like species, genus, and family.

4. **Final Answer**: The correct answer is **Option 4: In certain groups of organisms**.

---