Lichens show

Options

A. Commensalism
B. Mutualism
C. Parasitism
D. Mycorrhizal association.

Answer

To solve the question "Lichens show," we need to analyze the options provided: commensalism, mutualism, parasitism, and mycorrhizal association.

### Step-by-Step Solution:

1. **Understanding Lichens**: Lichens are composite organisms made up of a symbiotic relationship between a fungus and an alga (or cyanobacterium).

2. **Identifying the Type of Relationship**: In this relationship, both the fungus and the alga benefit from each other. The fungus provides a protective structure and absorbs moisture and nutrients from the environment, while the alga performs photosynthesis, producing food that both organisms can use.

3. **Analyzing the Options**:
- **Commensalism**: This is a relationship where one organism benefits while the other is neither helped nor harmed. This does not apply to lichens since both organisms benefit.
- **Mutualism**: This is a symbiotic relationship where both organisms benefit from each other. This accurately describes the relationship in lichens.
- **Parasitism**: In this relationship, one organism (the parasite) benefits at the expense of the other (the host). This is not applicable to lichens.
- **Mycorrhizal Association**: This refers to the symbiotic relationship between fungi and the roots of higher plants. While this is another form of mutualism, it is not the relationship that describes lichens.

4. **Conclusion**: Since lichens are formed through a mutualistic relationship between fungi and algae, the correct answer is **mutualism**.

### Final Answer:
Lichens show **mutualism**.

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