Option-1: 0oC is not the absolute zero temperature in Celsius. The Celsius scale starts at 0oC, which is the freezing point of water, so it cannot represent the absolute zero temperature.

Option-2: -100oC is not the absolute zero temperature in Celsius. It is a temperature below freezing point, but it is still above the absolute zero temperature.

Option-3: -273.15oC is the correct answer for the absolute zero temperature in Celsius. This is the point where all molecular motion stops, and it is the lowest possible temperature on the Celsius scale.

Option-4: -173.15oC is not the absolute zero temperature in Celsius. It is a temperature below freezing point but above the absolute zero temperature.

In conclusion, the correct answer is option-3 (-273.15oC), which represents the absolute zero temperature in Celsius.