Open loop systems and their examples:

An open loop system is a type of control system in which the output is not influenced by the current state of the system. In other words, the system does not have any feedback mechanism to adjust its behavior based on the output. Here is an explanation of each option and why option D, the execution of a program by a computer, is an example of an open loop system:

a) Household Refrigerator:
- A household refrigerator is not an example of an open loop system because it has a feedback mechanism to maintain the desired temperature inside the refrigerator.
- The refrigerator constantly monitors the temperature inside and adjusts the cooling mechanism accordingly to maintain the set temperature.

b) Respiratory system of an animal:
- The respiratory system of an animal is not an example of an open loop system because it operates on a feedback mechanism.
- The body continuously monitors the oxygen and carbon dioxide levels in the blood and adjusts the breathing rate accordingly to maintain a balance.

c) Stabilization of air pressure entering into the mask:
- The stabilization of air pressure entering into a mask is not an example of an open loop system because it requires feedback to ensure the air pressure is maintained at the desired level.
- If the air pressure deviates from the set level, a feedback mechanism is needed to adjust the flow of air and stabilize the pressure.

d) Execution of program by computer:
- The execution of a program by a computer is an example of an open loop system because there is no feedback mechanism to adjust the execution based on the output.
- The computer follows a predefined set of instructions without any monitoring or adjustment based on the output.
- It does not consider the result of each instruction to modify the subsequent instructions.

In conclusion, option D, the execution of a program by a computer, is an example of an open loop system because it operates without any feedback mechanism to adjust its behavior based on the output.