Of the Steps in Excitation-Contraction Below, Which Occurs Before the Others

Multiple Choice

Of the steps in excitation-contraction below, which occurs before the others?

A) Exposed actin sites bind with myosin cross bridges.
B) Sodium channels open in the fiber's membrane.
C) Calcium is released from the sarcoplasmic reticulum.
D) Troponin binds calcium.
E) Attachment of ATP allows for cross bridge detachment.