Correct Answer - Option 2 : 0.268

**Concept:**

The efficiency of the Carnot Engine:

\(η = \frac{{{T_H} - {T_L}}}{{{T_H}}} = 1 - \frac{{{T_L}}}{{{T_H}}}\)

The efficiency of the Carnot cycle is the function of source (T_{H}) and sink (T_{L}) temperature.

Carnot cycle efficiency depends upon the temperature range of operation.

**Calculation:**

**Given:**

TH = 373 K, TL = 273 K

Therefore, \(\eta =1-\frac{273}{373} = 0.268\)