The correct answer is: A. A.C.
When an electric current passes through water, it causes the water molecules to break down into hydrogen and oxygen gas. This is called electrolysis. The amount of bubbling that is observed depends on the strength of the electric current and the type of water. Tap water contains dissolved minerals, which can slow down the electrolysis process. Distilled water, on the other hand, does not contain any dissolved minerals, so electrolysis will occur more quickly.
Alternating current (A.C.) is a type of electric current that changes direction periodically. This is in contrast to direct current (D.C.), which flows in one direction only. A.C. is used in most homes and businesses because it is more efficient to transmit over long distances.
When A.C. current passes through water, it causes the water molecules to break down into hydrogen and oxygen gas. This is because the alternating current causes the water molecules to vibrate, which breaks them apart. The hydrogen and oxygen gas bubbles up to the surface of the water, which is what causes the bubbling that is observed.
D.C. current does not cause the water molecules to break down into hydrogen and oxygen gas. This is because the direct current does not cause the water molecules to vibrate. Therefore, if you observe bubbling when you pass an electric current through water, you can be sure that the type of supply is A.C.