First law of Thermodynamics does not tell about

The first law of thermodynamics states that energy can neither be created nor destroyed, only altered in form. For any system, energy transfer is associated with mass crossing the control boundary, external work, or heat transfer across the boundary.

The first law of thermodynamics is a law of conservation of energy. It does not specify the direction of the process. All spontaneous processes are processed in one direction only. The first law of thermodynamics does not deny the feasibility of a process reversing itself.

Hence the correct answer is (C) Feasibility of a process.