<prompt> If both the ala of the sacral bone are absent, pelvis is called as:Naegele pelvisRobert pelvisTriradiate pelvisRachitic pelvis  <response>: Ans. is b, i.e. Robert pelvisRef. Dutta Obs. 9e, p 326If one ala is absent-pelvis is called Naegles pelvis.If both ala of succumb are absent-pelvis is called as Roberts pelvis.Both are varieties of contracted pelvis and in both cesarean section is done. 