The hardest substance amonts the following is

Options

A. `Be_(2)C`
B. Graphite
C. Titanium
D. `B_(4)C`

Explanation

To determine the hardest substance among the given options, we need to analyze the properties of the substances mentioned. Here’s a step-by-step solution:

### Step 1: Identify the Substances
First, we need to identify the substances listed in the question. Although they are not provided, common candidates for hardest substances include diamond, boron carbide (B4C), and graphite.

### Step 2: Understand the Hardness of Diamond
Diamond is widely recognized as the hardest natural material. Its structure consists of a three-dimensional network of carbon atoms bonded by strong covalent bonds, which contributes to its exceptional hardness.

### Step 3: Analyze Boron Carbide (B4C)
Boron carbide (B4C) is known for its hardness and is often used in abrasives and armor. It is one of the hardest materials after diamond. Boron carbide has a unique structure that gives it high hardness and thermal conductivity while being an electrical insulator.

### Step 4: Consider Graphite
Graphite, although a form of carbon, is not hard. It has a layered structure where the layers can slide over each other easily, making it soft and brittle compared to diamond and boron carbide.

### Step 5: Compare the Hardness
Now, we compare the hardness of the substances:
- **Diamond**: Hardest known natural material.
- **Boron Carbide (B4C)**: Very hard, but not as hard as diamond.
- **Graphite**: Soft and brittle, not hard.

### Conclusion
Based on the analysis, the hardest substance among the options is **Boron Carbide (B4C)**, as it is harder than graphite and is one of the hardest materials after diamond.

### Final Answer
The hardest substance among the following is **Boron Carbide (B4C)**.

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