Final answer:
The minimum temperature for cleaning the milking system is approximately 140 degrees for the ultra-high-temperature (UHT) pasteurization method.
Step-by-step explanation:
The minimum temperature for cleaning the milking system depends on the method of pasteurization being used. One method, high-temperature short-time (HTST) pasteurization, exposes milk to a temperature of 72 °C for 15 seconds. Another method, ultra-high-temperature (UHT) pasteurization, exposes milk to a temperature near 140 °C for a few seconds.
The correct answer to your question would be 2) 140 degrees as it is the approximate temperature for the UHT pasteurization method.