Final answer:
Diagnosing electrical issues in appliances is a critical skill for an appliance repairer, as it allows for troubleshooting and fixing appliances that are not functioning properly.
Step-by-step explanation:
If you chose appliance repairer as your backup career, the most relevant skill from the options given would be a) Diagnosing electrical issues in appliances.
Electrical diagnostics are crucial for troubleshooting and fixing appliances. If a coffeemaker doesn't work when plugged into an electrical outlet, this might indicate an electrical problem with the outlet or the appliance itself.
By being able to diagnose and repair such electrical faults, an appliance repairer can ensure that all parts of the appliance are functioning correctly and safely.