what lines show the correct answer choice here please

Hi @Motunrayo-Bamgbose-Martins, Thanks for the question! Take a look at lines 43-45, which tell us that “the system reaches its critical state when the amount of sand added is balanced, on average, by the amount falling off the edge of the disk.” So the criticality of a sandpile is simply (E), which comes pretty directly from the text. Hope this helps! Feel free to ask any other questions that you might have.