Hydrogen has three isotopes : protium (¹H), deuterium (²H or D) and tritium (³H or T). They have nearly same chemical properties but different physical properties. They differ in :

Among the following, basic oxide is :

Among the given oxides of nitrogen ; N₂O, N₂O₃, N₂O₄ and N₂O₅, the number of compound/(s) having N - N bond is :

Which of the following oxoacids of sulphur contains "S" in two different oxidation states?