Which of these is correct for the non-uniform time-steps?(Note: t is the distance between the centroids of two temporal elements. t is the size of a temporal element. The superscript o indicates the older time step).

• A. ( delta t= frac{( Delta t- Delta t^o)}{2} )
• B. ( delta t= frac{( Delta t+ Delta t^o)}{2} )
• C. t= t
• D. t= t