Concept:Ripple is the unwanted residual alternating current (AC) variation that remains in the direct current (DC) output of a power supply.
Explanation:A power supply unit receives an alternating current source.
This AC voltage is converted into DC through rectification.
Rectification does not produce a perfectly smooth DC output.
The output still contains small fluctuations, known as ripple.
Therefore, the ripple arises from the process of converting AC to DC.
Hence, using an alternating current source is what causes the ripple.
Answer:A. using an alternating current source