31. When shall the parts be demagnetizec I after completion of examination? Kapan part harus di demagnetisasi setelah komplet pengujian? a. when required by code b. if the article will be magnetized c. any time is residua magnetism could interfere the subsequent process d. none of the above.

【Explanation】: The question is asking about the appropriate time to demagnetize parts after they have been examined. Demagnetization is a process used to reduce or eliminate the magnetic field in a material. This is important in many industrial and scientific applications where the presence of a magnetic field could interfere with the process or the accuracy of measurements. The options provided are:a. when required by codeb. if the article will be magnetizedc. any time is residual could interfere the subsequent processd. none of the above.Option 'a' suggests that demagnetization should be done when it is required by a code or regulation. This is a plausible answer as many industries have codes and regulations that dictate when certain processes should be performed.Option 'b' suggests that demagnetization should be done if the article will be magnetized. This is also a plausible answer as if an article is going to be magnetized, it would be important to demagnetize it first to ensure that the magnetization process starts from a non-magnetized state.Option 'c' is a bit unclear due to the phrasing, but it seems to suggest that demagnetization should be done at any time when residual magnetism could interfere with a subsequent process. This is also a plausible answer as residual magnetism can indeed interfere with many processes.Option 'd' suggests that none of the above options are correct.Given the information provided, the most appropriate answer seems to be 'a', demagnetize the parts when required by code. This is because having a code or regulation require