Basic unit or smallest taxon of classification is

Options

A. species
B. kingdom
C. family
D. variety

Explanation

### Step-by-Step Solution:

1. **Understanding Taxonomy**: Taxonomy is the science of classification of living organisms. It involves categorizing organisms based on their characteristics and relationships.

2. **Definition of Taxon**: A taxon (plural: taxa) is a group of one or more populations of organisms that form a unit. It can refer to any rank in the classification hierarchy.

3. **Hierarchy of Classification**: The classification system is organized in a hierarchical manner, which includes several ranks:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species

4. **Identifying the Smallest Taxon**: In this hierarchy, the smallest and most specific unit of classification is the species. It represents a group of individuals that can interbreed and produce fertile offspring.

5. **Conclusion**: Therefore, the basic unit or smallest taxon of classification is **species**.

### Final Answer:
The basic unit or smallest taxon of classification is **species**.

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