Above the Critical temperature (TC) of carbon dioxide, liquefaction of the gas is not possible.

Explanation:
- The critical temperature (TC) is the highest temperature at which a substance can exist as a liquid. Above this temperature, the substance cannot be liquefied by increasing pressure alone.
- Carbon dioxide has a critical temperature of approximately -78.5 degrees Celsius or -109.3 degrees Fahrenheit.
- When the temperature of carbon dioxide is above its critical temperature, it exists as a supercritical fluid, which exhibits properties of both a gas and a liquid.
- In the supercritical state, the gas cannot be liquefied by increasing pressure because the distinction between the gas and liquid phases is blurred.
- Unlike below the critical temperature, where increasing pressure can cause liquefaction, above the critical temperature, no amount of pressure can cause carbon dioxide to become a liquid.
- This is because the critical temperature represents a point where the substance's vapor pressure is equal to the pressure exerted on it. At this point, the substance cannot condense into a liquid regardless of pressure.
- As a result, carbon dioxide above its critical temperature will not undergo liquefaction, even if the pressure is increased significantly.
- It is important to note that above the critical temperature, carbon dioxide can still be compressed and its density increased, but it will not form a distinct liquid phase.
- The inability to liquefy carbon dioxide above its critical temperature has important applications in various fields, such as supercritical fluid extraction and supercritical fluid chromatography.
- In these processes, carbon dioxide is used as a supercritical fluid to extract or separate desired compounds due to its unique properties in the supercritical state.
- Therefore, option 'C' is the correct answer as it correctly states that liquefaction of carbon dioxide is not possible above its critical temperature.