Final Answer:
The interaction - chlorine + hydrogen = hydrogen chloride takes place with an explosion under conditions C: at maximum contact and in the dark.
Step-by-step explanation:
The reaction between chlorine (Cl₂) and hydrogen (H₂) to form hydrogen chloride (HCl) is an exothermic reaction. Explosions can occur when the reaction is initiated in the absence of light (dark conditions) and with maximum contact, allowing the reactants to mix thoroughly. Under these conditions (Option C), the reaction proceeds rapidly, producing a significant amount of heat and leading to an explosive reaction. In contrast, options A (stirring), B (in the cold), and D (maximum contact and direct sunlight) do not specifically describe the conditions that promote an explosion in the chlorine-hydrogen reaction.
Option C is the answer.