Hi there,
The Mitochondria is the power house of the cell. It provides energy for the cell therefore that is out.
The Ribosome breaks down and produces protein for the cell therefore that is out.
The Endoplasmic Reticulum allows protein to pass through in vacuoles therefore that's out as well.
The Nucleus acts as a brain controlling other organelles therefore it's the Nucleus.
So the answer is 3.
Hope this helps!
