Answer:

In a domestic baking oven, the temperature is controlled by a thermostat, not by series-parallel operation, voltage, or star-delta connections. The thermostat is an essential component of the oven that regulates the temperature to ensure that it remains within a desired range.

Thermostat:
The thermostat is a device that senses the temperature inside the oven and activates the heating element or switches it off accordingly. It consists of a temperature sensor, a control mechanism, and a switching device. The temperature sensor detects the current temperature, and the control mechanism compares it to the desired temperature set by the user. Based on this comparison, the switching device either turns on or off the heating element to maintain the desired temperature.

Importance of Temperature Control:
Temperature control is crucial in baking as it directly affects the outcome of the baked goods. Too high or too low temperatures can lead to undercooked or overcooked food. The thermostat ensures that the oven maintains a consistent temperature throughout the baking process, resulting in evenly baked and delicious food.

Other Options:
a) Voltage: Voltage is the electrical potential difference supplied to the oven. While voltage is necessary for the oven to function, it does not directly control the temperature.
c) Series-parallel operation: Series-parallel operation refers to the arrangement of electrical components in a circuit. It is not related to temperature control in an oven.
d) Star-delta connections: Star-delta connections are a method of connecting three-phase motors. They do not play a role in temperature control in an oven.

Conclusion:
The correct answer is option 'C' - Thermostat. The thermostat is responsible for controlling the temperature in a domestic baking oven and ensures that the desired temperature is maintained throughout the baking process.