Control center of the cell.

• A. Cytoplasm
• B. Ribosome
• C. Endoplasmic reticulum
• D. Nucleus

Answer: (D)

DNA inside the nucleus holds the instructions for making proteins and directing how the cell behaves. The nucleus acts as the control center by organizing which genes are turned on or off, guiding growth, metabolism, and division through gene expression. It’s surrounded by a double membrane with nuclear pores that regulate traffic between the nucleus and the rest of the cell. Other parts have important jobs too: the cytoplasm is the jelly-like environment where many reactions occur, ribosomes are the sites of protein assembly, and the endoplasmic reticulum helps build and transport proteins and lipids. But the nucleus is where the genetic blueprint is stored and managed, so it sits at the center of cellular control.