Which of These Statements Describes Foot Proteins

Which of these statements describes foot proteins

A) They span the gap between a lateral sac of the sarcoplasmic reticulum and the cell membrane.
B) They are believed to serve as Ca²⁺ channels.
C) They project from the thick filaments, bind to the thin filaments, and subsequently bend to pull the thin filaments inward toward the A band's centre during muscle contraction.
D) Each contains two subunits arranged in a specific pattern.