The membranous network inside a cell which forms the structural framework of a cell
A. Ribosome
B. Mitochondria
C. Chloroplast
D. Endoplasmic reticulum
E. Golgi apparatus

Hint: The cell wall is especially true composed of lipids and proteins. The key lipids are phospholipids and are arranged in an exceeding bilayer.

Complete step-by-step answer:
- Ribosome: It is the granular structure which was first observed under the electron microscope. They are composed of ribonucleic acid and proteins and are not covered by any membrane.
- Mitochondria: It is the sausage shaped or cylindrical with a diameter of 0.2 to 1.0 micrometre. Each mitochondrion is a double membrane structure with the outer membrane and inner membrane. They are called the powerhouse of the cell.
- Chloroplast: The photosynthesis in the plant body takes place by the presence of chloroplast. The chlorophyll is a photosynthetic pigment which absorbs energy from the sunlight.
- Endoplasmic reticulum: The membranous network which is present in the eukaryotic cell is the endoplasmic reticulum. The smooth endoplasmic reticulum and the rough endoplasmic reticulum are the two types of the endoplasmic reticulum. The smooth endoplasmic reticulum is the place where lipid synthesis takes place while the rough endoplasmic reticulum has ribosomes on their surface. It is also called the structural framework of the cell.
- Golgi apparatus: They consist of many flat, disc- shaped sacs. They are stacked parallel to each other. The Golgi cisternae are concentrically arranged near the nucleus.
Hence, the correct option is D.

Note: The endoplasmic reticulum helps in the movement of lipids and proteins which is required for the formation of the plasma membrane. The cisternae are attached by the cytoskeleton.