Answer with explanation:
Pottery is on a Kiln.
Unit of temperature can be Kelvin(°K) or Degree Celsius(°C) or Fahrenheit(°F).
Unit of time is second, minute and hour.
Rate of change of temperature of the pottery over time can be written as

Internationally , Kelvin is used as S.I unit of Temperature.
So,Yanin can use

as Rate of change of temperature of the pottery over time.