Final answer:
TCS food must be reheated to 165 degrees Fahrenheit if it's to be hot held, to ensure food safety by killing potential bacteria.
Step-by-step explanation:
The temperature to which TCS (Temperature Control for Safety) food must be reheated, if it will be hot held, is 165 degrees Fahrenheit. This is to ensure that any potential bacteria present are killed, reducing the likelihood of foodborne illness. It is essential that the recommended temperatures are strictly followed to maintain food safety.