Final answer:
In order to ensure that dishes are reaching the correct temperatures for sanitization in a mechanical dishwasher, it is important to calibrate the temperature gauges and sanitizer levels regularly.
Step-by-step explanation:
When you have a mechanical dishwasher, it is important to ensure that the dishes are reaching the correct temperatures for sanitization. To do this, you need to monitor the temperature gauges and sanitizer levels regularly. This means that option d) Calibrated regularly is the correct answer.