A form of which of the following non-metal is the hardest substance?

Options

A. phosphorus
B. sulphur
C. iodine
D. carbon

Explanation

To solve the question "A form of which of the following non-metals is the hardest substance?", we will follow these steps:

### Step 1: Identify the hardest substance
The hardest known natural substance is diamond.

### Step 2: Determine the composition of diamond
Diamond is an allotrope of carbon. This means that diamond is a different structural form of the element carbon.

### Step 3: Understand the structure of diamond
In diamond, each carbon atom is bonded to four other carbon atoms in a three-dimensional tetrahedral structure. This strong bonding and rigid structure contribute to the hardness of diamond.

### Step 4: Analyze the options provided
The options given are:
1. Phosphorus
2. Sulfur
3. Iodine
4. Carbon

### Step 5: Identify the correct answer
Since diamond is a form of carbon, the correct answer to the question is carbon.

### Final Answer
The hardest substance is a form of carbon (diamond).

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