Which of the Following Are Common Means by Which Binding

Multiple Choice

Which of the following are common means by which binding of an extracellular chemical messenger with a cell's receptor brings about a desired intracellular response?

A) opening or closing of specific channels to regulate ionic movement across the plasma membrane.
B) activation of an intracellular second messenger system.
C) alteration of protein shape and function as a result of phosphorylation.
D) only (a) and (b) above.
E) all of these answers.