Final answer:
A fluid phospholipid bilayer sandwiched between two layers of hydrophilic proteins describes the cell membrane. Phospholipids form a bilayer that serves as a selective barrier for the cell, and the nucleus is surrounded by two phospholipid bilayers.
Step-by-step explanation:
The question is asking about the structure referred to as a phospholipid bilayer sandwiched between layers of hydrophilic proteins, which correctly describes the cell membrane or plasma membrane of cells. This membrane acts as a barrier separating the internal environment of the cell from the external one. Within this membrane, phospholipids are arranged in two layers with their hydrophobic tails facing inwards and their hydrophilic heads facing the aqueous environments inside and outside the cell. The correct answer to the multiple-choice question is c) Cell membrane.
Answering a related question, the nucleus is the organelle that is surrounded by two phospholipid bilayers, known as the nuclear envelope. The phospholipid bilayer forms the basis of biological membranes, providing selective permeability essential for various cellular processes.