......................is soft and slippery with a basic pattern of hexagonal rings.

Answer

**Step-by-Step Text Solution:**

1. **Identify the Characteristics**: The question describes a substance that is "soft and slippery" and has a "basic pattern of hexagonal rings."

2. **Recall Knowledge of Carbon Allotropes**: Among the various allotropes of carbon, we need to consider which one fits these characteristics. The common allotropes of carbon include diamond, graphite, and fullerenes.

3. **Analyze Graphite**: Graphite is known for its unique structure. It consists of layers of carbon atoms arranged in hexagonal rings. Each carbon atom in graphite is bonded to three other carbon atoms, forming a planar hexagonal lattice.

4. **Understand the Layered Structure**: The layers in graphite are held together by weak van der Waals forces. This weak attraction allows the layers to slide over one another easily, which is why graphite is slippery.

5. **Conclude the Answer**: Based on the characteristics described in the question and the analysis of graphite's structure, the answer to the fill-in-the-blank question is "graphite."

**Final Answer**: Graphite

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