Lichens are

Options

A. commensal
B. dual/composite organism
C. saprophyte
D. all the above

Answer

**Step-by-Step Solution:**

1. **Understanding Lichens**: Lichens are unique organisms that arise from a symbiotic relationship between two different types of organisms: fungi and either algae or cyanobacteria.

2. **Composition of Lichens**: In this symbiotic relationship, the fungi provide a protective structure (the hyphae) in which the algae or cyanobacteria can live. This structure helps retain moisture and offers a safe environment for the photosynthetic partner.

3. **Function of Each Partner**: The algae or cyanobacteria perform photosynthesis, producing carbohydrates (food) that are shared with the fungi. In return, the fungi provide shelter and protection to the algae or cyanobacteria, creating a mutually beneficial relationship.

4. **Classification of Lichens**: Given the nature of this relationship, lichens are classified as composite organisms or dual organisms. This classification highlights the interdependence of the two partners involved.

5. **Conclusion**: Therefore, lichens can be accurately described as dual or composite organisms due to their symbiotic association between fungi and either algae or cyanobacteria.

**Final Answer**: Lichens are dual or composite organisms.

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