The answer is: a. neutral charge, nonpolar, and hydrophobic.
Phospholipids are lipids and major component of all cell membranes.
In phospholipid layer in cell membrane, there are hydrophilic heads (polar part of the layer) and hydrophobic tails (nonpolar part of the layer).
The structure of the phospholipid molecule is formed of two hydrophobic fatty acid tails and a hydrophilic head consisting of a phosphate group.
1) Small, non-polar molecules diffuse easily through this layer, no energy is required, this is passive transport.
2) Polar molecules cannot diffuse through phospholipid layer using passive transport, because hydrophobic tails does not allow that (polar molecules are reppeled), energy is required for that, this is active transport.
