In class 3 and class 5 cavity  preparation  retention grooves are given:: (A) Over dentinal wall., (B) Over facial and lingual walls., (C) Over axial wall, (D) All of the above
Answer is A. In class III class IV preparations the external walls diverge outwards to provide string enamel margins and therefore Retention Coves (on 3-point angles) or Retention grooves (on axio gingival line angle) are prepared in the dentinal walls to provide the retention form.