Sulphuric acid is a strong and highly corrosive acid that is commonly used in various industrial processes. It has several properties that make it unique and useful in different applications. However, one of the properties listed in the options is not true for sulphuric acid.

Dehydrating Agent:
- Sulphuric acid is a strong dehydrating agent, meaning it has the ability to remove water molecules from substances.
- It reacts with water to form sulphuric acid, which can be seen as a vigorous reaction with the evolution of heat and steam.
- This property is widely utilized in various chemical processes where water needs to be removed.

Lewis Acid:
- A Lewis acid is a substance that can accept an electron pair and form a covalent bond.
- Sulphuric acid can act as a Lewis acid due to the presence of the sulfate ion (SO4^2-) which can accept an electron pair.
- This property allows sulphuric acid to participate in various chemical reactions as an electron acceptor.

Cannot Char Carbohydrates:
- This property is not true for sulphuric acid. Sulphuric acid can char carbohydrates, which means it can cause the breakdown and blackening of carbohydrates when in contact with them.
- This charring reaction is an example of a dehydration reaction, where sulphuric acid removes water molecules from the carbohydrate structure, leaving behind a charred residue.

Dense and Oily:
- Sulphuric acid is a dense and oily liquid.
- It has a high density compared to water, which is why it sinks when mixed with water.
- The oily texture is due to its high viscosity, which gives it a thick and slippery consistency.

In summary, the correct answer is option C: Sulphuric acid can char carbohydrates. This property is not true for sulphuric acid as it can indeed char carbohydrates through a dehydration reaction.