Which Statement Concerning Cross Bridges Is INCORRECT

Which statement concerning cross bridges is INCORRECT?

A) Cross bridges are the globular heads of myosin molecules.
B) Cross bridges have actin binding sites that are normally covered by troponin and tropomyosin except during excitation-contraction coupling.
C) Cross bridges bind with actin and then bend to pull the thin filaments inward during contraction according to the sliding filament mechanism.
D) Mg2+ is necessary to bind ATP to the cross bridge.