Answer:
The given blank can be filled with the endoplasmic reticulum.
Step-by-step explanation:
A composite network of tubular membranes found inside the cytoplasm of the eukaryotic cell that is basically involved in the transportation of substances is known as ER or endoplasmic reticulum.
Generally, the ER is the system of transportation in the eukaryotic cell and can be basically illustrated as a membrane network found inside the cytoplasm of the cells taking part in the process of modification, synthesis, and transport of cellular substances.