The cell membrane is considered selectively permeable because

A) it is made of water, proteins, and amino
acids.

B) it is only found in multicellular organisms.

C) it separates the cell from its outside
environment.

D) it lets certain substances pass through but
not others.

The membrane is selectively permeable because substances do not cross it indiscriminately. Some molecules, such as hydrocarbons and oxygen can cross the membrane. Many large molecules (such as glucose and other sugars) cannot. Water can pass through between the lipids. Ions such as H+ or Na+ cannot.

So I think the answer is D) It lets certain Substances pass through but not others.

Sodium is the answer