Which of the Following Is True About Gene Regulation in Cells

Which of the following is true about gene regulation in cells?

A) Gene expression is nonvariable for cells;it is the same for all cells of the same type.
B) Gene expression is highly variable;it changes for many different reasons throughout the life of a cell.
C) Gene expression is set by internal factors early in the life cycle of a cell and remains the same from that point forward.
D) Gene expression is set by external factors early in the life cycle of a cell and remains the same from that point forward.