The Arduino UNO uses a voltage regulator that provides two common output voltages:

1. 5V - This is the primary output voltage for powering the microcontroller and other components on the board.
2. 3.3V - Some boards (like Arduino Due) have a 3.3V regulator, but on the standard Arduino UNO, this is usually used for peripherals.

However, the main voltage output from the voltage regulator is 5V.

Correct Answer:

(C) 5V and 3.3V