I think the main cause would be water
The answer to this question would be because phospholipid is polar has <span>a </span>charge.
Since phospholipid is polar, it can attract molecule with a charge. That will cause the molecule cant move easily pass the membrane. The hydrophobic molecule doesn't have charge, so the molecule can pass through the phospholipid membrane if it small enough.
Answer-
I think it’s D.
I hope you get it right!