Two molecules that can cross a lipid bilayer without from membrane proteins are o2 and co2. what property allows this to occur?

Two molecules that can cross a lipid bilayer without help from membrane proteins are oxygen and carbon dioxide. The property that allows this to happen is that both oxygen and carbon dioxide molecules are nonpolar which means that they can pass easily through the hydrophobic part of the membrane. The lipid bilayer is present in all cell membranes. It consists of two layers of the fat cells which are arranged into two sheets. It functions as a barrier which marks the boundaries of the cell. The inner part of a lipid bilayer is nonpolar since it is composed of the hydrophobic end of the phospholopids. 

The answer for this question is d. none of these