The carious lesion marked by the arrow represents:: (A) Forward caries, (B) Backward caries, (C) Recurrent caries, (D) Smooth surface caries
Answer is C. Recurrent Caries:
Recurrent caries is that type which occurs in the. It is usually due to inadequate extension of the original restoration, which favors retention of debris, or to poor adaptation of the filling material to the cavity, which produces a ‘leaky margin’. 
Ref: Shafer's textbook of oral pathology 7th edition page 445