7. HMG-CoA reductase is the key regulatory site in cholesterol synthesis. Which of the following statement about the regulatory mechanisms of HMG-CoA reductase is TRUE? (A) Phosphorylation by cAMP-dependent kinase activates HMG-CoA reductase, (B) A high AMP:ATP ratio leads to activation of HMG-CoA reductase, (C) High cholesterol level increases the half-life of HMG-CoA reductase, (D) High cholesterol level increases HMG-CoA reductase gene expression, (E) HMG-CoA reductase phosphatase can activate HMG-CoA reductase.