The correct option is: (d) Endoplasmic reticulum
Explanation:
Endoplasmic reticulum functions as cytoskeleton or intracellular and ultrastructural skeletal framework by providing mechanical support to colloidal cytoplasmic matrix. Proteins and enzymes synthesised by ribosomes enter the channels of rough endoplasmic reticulum both for intracellular use as well as extracellular transport.