Answer :

In the food industry, maintaining the accuracy of thermometers is crucial to ensure food safety and proper handling. Calibrating thermometers on a regular basis is a key practice that ensures the readings are accurate and reliable.

Different scenarios might necessitate thermometer calibration, such as:
- Before each shift
- When there are changes in temperature readings
- After the thermometer has been dropped or exposed to extreme temperature changes

These specific scenarios require prompt calibration to maintain accuracy. However, for routine calibration practices, there is a standard frequency recommended.

Out of the provided options:
1. Weekly
2. Monthly
3. Quarterly
4. Annually

The option that aligns most closely with routine calibration practices in the industry is Weekly. Calibrating thermometers on a weekly basis ensures regular checks are performed without being too infrequent, thus maintaining the accuracy needed for food safety consistently.

Therefore, the most suitable practice for thermometer calibration in the food industry, considering regular routines, is to calibrate Weekly.