Which of the Following Statements Regarding Contraction in Skeletal and Smooth

Multiple Choice

Which of the following statements regarding contraction in skeletal and smooth muscle is TRUE?

A) In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding directly to myosin.
B) In skeletal muscle,calcium ions bind to a regulatory protein on thin filaments;in smooth muscle,calcium ions bind to a regulatory protein on thick filaments.
C) In skeletal muscle,calcium initiates contraction by binding to myosin light-chain kinase,while in smooth muscle calcium initiates contraction by binding directly to tropomyosin.
D) In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding to calmodulin.
E) All of the choices are true.