A quick supply of chlorine​ gas may be made by reacting crystals of $KMn{{O}_{4}}$ with a concentrated solution of
A. Potassium chloride
B. Sodium chloride
C. Bleaching powder
D. Hydrochloric acid

Hint: Chlorine is a gaseous substance of the halogen group. It can be liberated easily by the reaction of a strong oxidising agent potassium permanganate with hydrochloric acid.

Complete Step by Step Answer:
When a strong oxidising agent potassium permanganate or $KMn{{O}_{4}}$ reacts with hydrochloric acid, a strong acid a salt like compound named as potassium chloride, a another salt like compound named as manganese chloride along with chlorine gas and water are formed as products. The reaction can be given as follows:
$2KMn{{O}_{4}}+16HCl\to 2KCl+2MnC{{l}_{2}}+5C{{l}_{2}}+8{{H}_{2}}O$

Thus in this reaction two moles of a strong oxidising agent potassium permanganate or $KMn{{O}_{4}}$ reacts with sixteen moles of hydrochloric acid, a strong acid to form two moles of a salt like compound named as potassium chloride, two moles of a another salt like compound named as manganese chloride along with five moles of chlorine gas and eight moles of water are.

Thus we can write that a quick supply of chlorine​ gas may be made by reacting crystals of $KMn{{O}_{4}}$ with a concentrated solution of hydrochloric acid.
Thus the correct option is D.

Note: As potassium permanganate is a highly oxidising agent, it acts as a disinfectant to treat skin infections. It is very effective in treating a fungal infection. It is also used in chemistry labs as a reagent to calculate the amount of substance that can be oxidised in a sample.