The catalyst used in contact process is:

Explanation:

Contact process:

By contact process, H2SO4(Sulphuric acid) is prepared in presence of V2O5(Vanadium oxide).                  
                          
 SO2 (g)           +                   1/2O2 (g)                                     SO3 (g)
                    (Sulphur dioxide)                  (Oxygen)                          (Sulphur trioxide)

                                                                                                                   
The catalyst in the above reaction is V2O5.

Final Answer:
Hence, Option (C) is correct.