Correct answer is (d) 2.7V to 5.5V
Best explanation: The operating voltage of the Atmega32U4 is 2.7V to 5.5V. Provide any voltage lower than that and the chip will not function. But however, if any voltage higher than the rated voltage is provided there is a chance of damaging the IC physically. So, under no circumstance should this chip be provided a voltage more than the rated voltage.