Solution :
Disulphuric acid $$\left( {{H_2}{S_2}{O_7}} \right)$$ is called oleum or fuming sulphuric acid. It is strongest oxidising agent and more powerful dehydrating agent.
Releted MCQ Question on Inorganic Chemistry >> P - Block Elements
Releted Question 1
The reddish brown coloured gas formed when nitric oxide is oxidised by air is