How many times per second does AC alternate between DC positive and DC negative?

In alternating current (AC) systems, the frequency is typically measured in hertz (Hz), which indicates the number of cycles that occur per second. In North America, the standard frequency for AC power supply is 60 Hz, meaning that the current alternates direction 60 times each second. This means that during each cycle, the current flows in one direction and then reverses, moving in the opposite direction.

The other answers refer to different frequencies that are used in various parts of the world, or they are simply incorrect in this context. For example, many countries use a 50 Hz system, which is common in Europe and other regions, but it is not applicable here when focusing on the North American standard. Thus, acknowledging the North American electrical standard, the correct choice reflects that AC indeed alternates between DC positive and DC negative 60 times per second.