In the questions given below, select the one which is different from the other three responses.

Now, we check each options.

Option (a): Petrol - Liquid fuel

Option (b): Diesel - Liquid fuel

Option (c): Kerosene - Liquid fuel

Option (d): LPG (Liquefied Petroleum Gas) - Gas (stored as liquid under pressure)

So, option a, b, and c are liquid fuels. But option (d): LPG is a gas (under pressure), different in form and composition.

Thus, correct option is (d).