Which of the Following Best Explains Why a Neuron and a Pancreatic

Which of the following best explains why a neuron and a pancreatic cell isolated from the same individual contain different sets of proteins?

A) The set of genes in each cell type are different, therefore, they express different proteins.
B) Each cell type needs different proteins and, therefore, they break down proteins they don't need.
C) Each cell type contains different regulatory proteins and, therefore, they express different proteins.
D) The genes in each cell type have different promoters and, therefore, they respond to different regulatory proteins.