The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order of low to high permeability from left to right. Your answer would be a six-digit number composed of digits 1 to 6, e.g. 123456.
(A) O²
(B) ATP
(C) RNA oligonucleotide
(D) Na⁺
(E) Glucose
(F) Urea