Option D (All of the above) is correct because the textbook explicitly mentions all three methods for disaggregating cells. The context states that for preparation of primary cultures, tissues undergo 'mechanical or enzymatic disaggregation' (supporting options A and B). Additionally, for passaging adherent cells, the text mentions 'enzymatic activity (trypsin, trypsin + EDTA, etc.) or mechanical means (using cell scraper, shaking, vigorous pipetting, etc.)'. EDTA is a chelating agent, which supports option C. Since physical disruption (mechanical means), enzymatic digestion (enzymes like trypsin, collagenase), and chelating agents (EDTA) are all mentioned as methods for cell disaggregation/detachment, the correct answer is 'All of the above'.