The outer layer of a cell that acts as a gatekeeper to a cell is the

The outer layer of a cell that acts as a gatekeeper to a cell is the Cell Membrane or Plasma Membrane.

The cell membrane made up of mostly phospholipids and proteins and is known as selectively permeable membrane as it allows the entry of some selective molecules into it.

The plasma membrane is the layer present between  the cell and its external  environment. As the gatekeeper takes care of entry, cell membrane also regulates the molecules that enters and exits the cell from external environment.

Cells membrane helps in maintaining appropriate amount of molecules to function inside them.

Hence, the correct option is Cell Membrane.

the median of the data is 4.5.

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully