Vesicle is involved in the transportation of proteins, lipids across the cell. Also, it transports cellular secretions out of the cell. Therefore, option A is incorrect.
Nucleus regulates the cellular processes. Therefore, option B is incorrect.
Endoplasmic reticulum is involved in lipid synthesis and in correct and functional folding of newly formed protein molecules. Therefore, option C is incorrect.
Cytoskeleton is a network of fibrils present all over the cell. It is a dynamic structure present in cell i.e., the fibrils present in cytoskeleton are broken down and re-joined according to necessity of the cell. This way, it can change cell shape and carries out movement of the cell and internal organization. Therefore, option D is correct.