The permeability of a membrane to a particular molecule is related to two variables. Which two variables is it related to and what is the relationship?

a) It is directly proportional to lipid solubility and inversely proportional to the size of the molecule.
b) It is directly proportional to both lipid solubility and molecular size.
c) It is inversely proportional to both lipid solubility and molecular size.
d) It is inversely proportional to lipid solubility and directly proportional to the size of the molecule.