The Following Table Shows Which of These Four Genes Are

The following table shows which of these four genes are on or off in three different cell types. Why is the expression of the rRNA gene so different from the expression of the other genes in the table?

A) rRNA is required for the proper functioning of all cells, but the products of the other genes are only essential to the function of one cell type.
B) rRNA is easier to produce than the products of the other genes.
C) The rRNA gene is found in the genomes of all three cell types, but the other genes are only found in the genomes of their specific cell type.
D) rRNA is needed at all stages of the cell cycle, but the products of the other genes are only needed during cell division.