Answer:
Option A, hydrophilic/hydrophobic forces
Explanation:
The cytoplasmic membrane consists of phospholipids which have both the hydrophilic and hydrophobic regions and hence are amphipathic in nature. Due to this structural complexity, phospholipids produces barrier both at the interior and exterior of cell and hence form a membrane bilayer under suitable conditions. For instance when it is in water, it arrange itself in a way that their hydrophobic tails lie at the inner side and hydrophilic heads face outer side.
Hence, option A is correct
The answer would be sewage treatment plants
