Which of the following statements about myosin is true:
A. In vitro, myosin assembles spontaneously into the thin filaments
B. Myosin is an ATPase that binds polymerized actin
C. Myosin is composed of two polypeptide chains, one of which forms an alpha (\alpha )-helical coiled-coil and the other a globular head
D. Myosin is bound to the Z-disk
