Option 1 states that the absolute zero is 0°C. However, this is not correct. The absolute zero is a temperature below which it is not possible to go. The Celsius scale starts at 0°C, which is the freezing point of water, so it cannot represent the absolute zero.

Option 2 states that the absolute zero is -273 K. This is the correct answer. The Kelvin scale is an absolute temperature scale, where 0 K represents the absolute zero. In this scale, temperature is measured from absolute zero, with no negative values. Therefore, -273 K represents the absolute zero.

Option 3 states that the absolute zero is -273 °C. This is incorrect. The Celsius scale does not have an absolute zero point. It is based on the freezing and boiling points of water, with 0°C representing the freezing point and 100°C representing the boiling point at standard atmospheric pressure.

Option 4 states that the absolute zero is -300 °C. This is not accurate. As explained earlier, the Celsius scale does not have an absolute zero, so -300 °C cannot represent the absolute zero.

In conclusion, the correct answer is option 2, which states that the absolute zero is -273 K.