Which characteristic placed the fungi in a separate kingdom?

Options

A. Cell wall composition
B. Cell wall structure
C. Nutrition
D. Nuclear membrane

Answer

### Step-by-Step Solution:

1. **Understanding the Classification of Fungi**: Initially, fungi were classified under the plant kingdom due to some similarities. However, further research revealed distinct characteristics that warranted their classification into a separate kingdom.

2. **Identifying Key Characteristics**: The primary characteristic that differentiates fungi from plants is the composition of their cell walls. While plant cell walls are primarily made of cellulose, fungi have cell walls made of chitin.

3. **Cell Wall Composition**: Chitin is a significant component found in the cell walls of fungi. This composition is rigid and provides structural support, which is different from the cellulose found in plants.

4. **Nutritional Differences**: Fungi also have a unique mode of nutrition, as they are heterotrophic organisms that absorb nutrients from their surroundings, unlike plants that perform photosynthesis.

5. **Conclusion**: The defining characteristic that placed fungi in a separate kingdom is their cell wall composition, specifically the presence of chitin.

### Final Answer:
The characteristic that placed fungi in a separate kingdom is **cell wall composition** (specifically, the presence of chitin).

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