Question

which organelle can be compared to a security guard who decides whom may enter a building and whom may not? cell membrane cytoplasm endoplasmic reticulum mitochondrion

Explanation:

The cell membrane controls the movement of substances in and out of the cell, just as a security guard decides who can enter and who cannot enter a building. The other organelles have different functions - mitochondria are for energy - production, endoplasmic reticulum is involved in protein and lipid synthesis, and cytoplasm is the fluid - like substance that fills the cell.

Answer:

cell membrane