<prompt> In class 3 and class 5 cavity preparation retention grooves are given:Over dentinal wall.Over facial and lingual walls.Over axial wallAll of the above  <response>: 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. 