Final answer:
A motor may burn out due to overloads, high ambient temperatures, and poor ventilation; all these factors can cause excessive heating, which the motor may not be able to manage.
Step-by-step explanation:
The motor may burn out due to overloads, high ambient temperatures, and poor ventilation. Overloads occur when a motor is required to perform beyond its capacity, leading to excessive currents running through the motor, which generates more heat than the motor can dissipate. High ambient temperatures refer to the surrounding environmental temperature, which, if too high, can prevent the motor from cooling properly. Poor ventilation inhibits the removal of heat from the motor. All of these factors contribute to an increase in the motor's temperature, potentially leading to a burnout. Therefore, the correct answer is D. All of the above.