How do combinations of transcription regulators contribute to the differentiation of cell types?

• A. They randomly activate genes, leading to unpredictable cell differentiation.
• B. They prevent any gene expression, maintaining cells in an undifferentiated state.
• C. They ensure that all genes are expressed equally in all cell types.
• D. They control sets of genes responsible for differentiating cells into specific types, such as kidney cells.

Answer: (D)