The substance W is a folssil fuel . It occurs deep below the ground in certain areas of the earth. Another fossil fuel X is found trapped above the deposits of W. When W is subjected to a process called Y, then a number of different products are collected at different temperature ranges which are put to different uses. A special grade of product Z obtained in this way is used as aviation fuel in jet aeroplanes.
d) Name the product Z.

Explanation

To solve the question step by step, we can break it down as follows:

### Step 1: Identify Substance W
- **Substance W** is described as a fossil fuel that occurs deep below the ground. The most common fossil fuel found deep underground is **petroleum**.

### Step 2: Identify Substance X
- **Substance X** is another fossil fuel found trapped above the deposits of W. In the context of petroleum, the fossil fuel that is typically found above petroleum deposits is **natural gas**.

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