A division is formed by combining several :-

Options

A. Orders
B. Families
C. Classes
D. Tribes

Answer

To answer the question "A division is formed by combining several:", we need to analyze the options provided and understand the taxonomic hierarchy in biology, particularly in plant taxonomy.

### Step-by-Step Solution:

1. **Understand Taxonomic Ranks**:
- In biological classification, organisms are grouped into hierarchical ranks. The major ranks in descending order are: Kingdom, Division (or Phylum for animals), Class, Order, Family, Genus, and Species.

2. **Identify the Meaning of 'Division'**:
- In the context of plant taxonomy, a 'division' is equivalent to a 'phylum' in animal taxonomy. It represents a higher taxonomic category that groups together related classes.

3. **Evaluate the Options**:
- **Option A: Orders**: An order is a group of families. Therefore, it cannot combine to form a division.
- **Option B: Families**: A family is a group of related genera (plural of genus). Thus, families do not combine to form a division.
- **Option C: Classes**: A division is indeed formed by combining several interrelated classes. This is the correct option.
- **Option D: Tribes**: A tribe is a rank below family and cannot combine to form a division.

4. **Conclusion**:
- Based on the analysis, the correct answer to the question is **C: Classes**. A division is formed by combining several classes in the context of plant taxonomy.

### Final Answer:
A division is formed by combining several **classes**.