The correct answer is: B. Spontaneous oxidation-reduction reaction
A dry cell is a type of electrochemical cell that uses a chemical reaction to generate an electric current. The cell consists of two electrodes, a cathode and an anode, which are separated by an electrolyte. The cathode is made of zinc, and the anode is made of manganese dioxide. The electrolyte is a paste of ammonium chloride and zinc chloride.
When the cell is connected to an external circuit, a chemical reaction occurs between the zinc and the manganese dioxide. The zinc is oxidized, and the manganese dioxide is reduced. This reaction produces an electric current.
The working of a dry cell is based on a spontaneous oxidation-reduction reaction. An oxidation-reduction reaction is a chemical reaction in which one substance loses electrons (oxidation) and another substance gains electrons (reduction). In a dry cell, the zinc is oxidized, and the manganese dioxide is reduced. This reaction produces an electric current.
The other options are incorrect because:
- A decomposition reaction is a chemical reaction in which a compound is broken down into its constituent elements.
- A combination reaction is a chemical reaction in which two or more substances combine to form a new substance.
- Electrolysis is a process in which an electric current is used to cause a chemical reaction to occur.