Which have different numbers of electron? A) different ions of an element
B) different isotopes of an element
C) the nucleus of an element
D) each of the atoms of an element

The list of  four (4) common passageways for non-water molecules for entering and exiting the cells are the following; 

Endocytosis
Exocytosis
Facillitated Diffusion
Active Transport

Endocytosis is a form of active transport  in which a substance gains entry into a cell without passing through the cell membrane. Exocytosis is a form of active transport by which a cell transports secretory products through the cytoplasm to the plasma membrane. Facilitated Diffusion also called as facilitated transport is a form of transport of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins.Active Transport is a mechanisms that require the use of the cell's energy, usually in the form of adenosine triphosphate (ATP)