The correct answer to the question is b. dry cell.
Explanation:
1. A dry cell is a source of constant electric current commonly used in household items like flashlights, remote controls, and portable electronic devices.
2. Inside a dry cell, chemical reactions occur between the electrolyte and the electrodes, producing a steady flow of electrons, which results in a constant electric current.
3. Unlike a switch that controls the flow of current, a transformer that changes the voltage of the current, or a coulomb which is a unit of electric charge, a dry cell actually generates the constant electric current itself.
In summary, a dry cell is a reliable and convenient source of constant electric current due to the chemical processes happening within it, making it a suitable choice for powering various everyday devices.
