Final answer:
O-linked oligosaccharides attached to serine residues are assembled wholly within the Golgi complex.
Therefore, the correct answer to the question is option 3.
Step-by-step explanation:
The oligosaccharide chain that is assembled wholly in the Golgi complex is the O-linked oligosaccharides attached to serine residues. N-linked oligosaccharides begin their assembly in the rough endoplasmic reticulum (RER) before being further modified in the Golgi. However, the synthesis of O-linked oligosaccharides, which are attached through the hydroxyl group of serine or threonine residues, occurs entirely within the Golgi apparatus.
Therefore, the correct answer to the question is option 3.