Which of the following describes alternating current?

Alternating current (AC) is defined by the periodic reversal of the direction of electron flow. In a true AC circuit, the current flows in one direction (positive), decreases to zero, and then reverses to flow in the opposite direction (negative). If a current fluctuates but only moves between a positive voltage and zero, or a negative voltage and zero, it never actually reverses direction. This type of waveform is considered a pulsating direct current (DC), not alternating current. Therefore, true AC must cross the zero line and alternate between both positive and negative directions. Because pulsing DC is not AC, the "All these answers are correct" option is false.