What structural change occurs during telophase of mitosis?

During telophase of mitosis, one of the key events is the reformation of the nuclear envelope around each set of chromosomes at opposite poles of the cell. This is crucial because, at this stage of the cell cycle, the separated sister chromatids have reached their respective poles, and their decondensation begins, leading to the return from the condensed chromosomal structure back to the less compact chromatin structure. The reformation of the nuclear envelope is a critical aspect as it signifies the end of mitosis and the beginning of the next phase, cytokinesis, where the cytoplasm will eventually divide to form two separate daughter cells. Thus, the correct answer reflects this essential structural change that facilitates the maintenance of genetic integrity in the daughter cells following cell division.