Selective permeability means that specific molecules or ions can move through the cell membrane by passive transport or active transport as seen with

With microscope.

Explanation:

Every cell has a selective permeable membrane in which smaller molecules can pass whereas bigger molecules stays outside the cell which can be seen in the cell with the use of microscope because it only occurs inside the cell. The movement of ions or molecules in the cell through a semi permeable membrane is called Osmosis. The movement of ions or molecules sometime needs energy we called it active transport and sometimes it moves without the use of energy is known as passive transport.

yes it is weird but true