The correct answer is: B. 1.2 V
Alkaline batteries are a type of primary cell battery that uses an alkaline electrolyte. They are commonly used in small portable devices such as flashlights, toys, and calculators. Alkaline batteries have a higher voltage than carbon-zinc batteries, which makes them a good choice for devices that require a lot of power.
The average charging voltage for an alkaline cell is 1.2 volts. This means that if you charge an alkaline cell with a voltage higher than 1.2 volts, you could damage the battery. If you charge an alkaline cell with a voltage lower than 1.2 volts, the battery will not charge properly.
Option A is incorrect because the average charging voltage for an alkaline cell is 1.2 volts, not 1 volt.
Option C is incorrect because the average charging voltage for an alkaline cell is 1.2 volts, not 1.7 volts.
Option D is incorrect because the average charging voltage for an alkaline cell is 1.2 volts, not 2.1 volts.