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

The correct answer would be the cell membrane.

The plasma membrane or cell membrane is a semi-permeable membrane which forms the outer covering of the cell.

This membrane is made up of a phospholipid which provides it with its semi-permeable nature.

Due to its semi-permeable nature, it controls the movement of substances inside and outside the cell.