NEET UG CHEMISTRY MCQ: HYDROGEN

When a substance $A$ reacts with water it produces a combustible gas $\mathrm{B}$ and a solution of substance $\mathrm{C}$ in water. When another substance $\mathrm{D}$ reacts with this solution of $\mathrm{C}$, it also produces the same gas $\mathrm{B}$ on warming but $\mathrm{D}$ can produce gas B on reaction with dilute sulphuric acid at room temperature. A imparts a deep golden yellow colour to a smokeless flame of Bunsen burner. A, B, C and D respectively are