Which of the Following Best Describes the Function of the Sacrotuberous

Which of the following best describes the function of the sacrotuberous and sacrospinous ligaments?

A) They prevent excessive counternutation of the sacrum on the innominates.
B) They become most taut with end range of hip extension to effectively lock the sacrum and innominates together.
C) They counterbalance the trunk forces that flex the sacral promontory.
D) They form the superior border of the lesser sciatic foramen.