Which Statement Is True Regarding Retention of Pins

Which statement is true regarding retention of pins?

A) In general, three pins are inserted to replace each missing cusp.
B) The retention pin has deep threads that grip the dentin when screwed into tooth structure.
C) Pins are always 0.023 mm in diameter and extend 2 mm into tooth structure.
D) Pins are placed into the root canal of the tooth.