Potassium manganate `(K_2MnO_4)` is formed when
A. Chlorine is passed into aqueous `KMnO_(4)` is formed when
B. manganese dioxide is fused with potassium hydroxide in air
C. formaldehyde reacts with potassium permanganate in presence of a strong alkali
D. potassium permanganate reacts with conc. Sulphuric acid.