Lichens are symbiotic.

Explanation

### Step-by-Step Solution:

1. **Understanding Symbiosis**: Begin by defining symbiosis. Symbiosis is a close and long-term interaction between two different biological species, where both organisms benefit from the relationship.

**Hint**: Remember that symbiosis involves mutual benefits for both organisms involved.

2. **Identifying the Organisms in Lichens**: Lichens are formed by the symbiotic association of two different organisms: algae and fungi.

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