Among the following the plain of least pelvic dimension is:

Ans-C (Outlet) Ref: Dutta, 6th ed, p. 91The obstetrical outlet extends from lower border of the symphysis pubis to tip of ischial spines and posteriorly to meet the tip of sacral vertebrae, this plane is known as the plane of least pelvic dimension or narrow pelvic planeIt roughly corresponds to the levator ani musclesIt is the plane at which internal rotation occurs. It is the landmark used for pudendal nerve block. Diagonal conjugated Diametres Diagonal conjugateTrue conjugate- 12 cm- 11 cm (Anatomical conjugate, Conjugate vera) Obstetric conjugate- 10 cmObstetric conjugate =-5-2)Comconjugatedrements of the diameter of the inlet, cavity, and outlet BRIMCAVITYOUTLETAP111213Oblique1212 Transverse131211The plane of greatest pelvic dimension:Post surface of pubic symphysis to the junction of the second and third sacral vertebraThe plane of least pelvic dimension:The lower border of pubic symphysis to the tip of ischial spines and the tip of 5th sacral vertebra.Sacrocotyloid diameter-9.5 cmWaste space of Morris - Should not exceed 1 cmSubpubic angle - 85degPelvic axisAnatomical (curve of earns)ObstetricalLithotomy position A-P diameter of outlet increases by (1.5-2 cm)