Which of the Following Most Accurately Describes Selective Permeability

Which of the following most accurately describes selective permeability?

A) Molecules below a certain molecular weight cross the membrane easily.
B) Lipid-soluble molecules pass through the membrane.
C) There must be a concentration gradient for molecules to pass through the membrane.
D) The ability of a molecule to pass through a membrane depends on transport and channel proteins present in the membrane.