Correct Answer: A number of possible explanations for why manhole covers are round include : 1 A round manhole cover cannot fall through its circular opening, whereas a square, rectangular, or oval manhole cover could fall in if it were inserted diagonally in the hole 2 Circular covers don’t need to be rotated or precisely aligned when placing them on the opening 3 A round manhole cover is easily moved and rolled 4 Human beings have a roughly circular cross-section 5 Round tubes are the strongest shape against the compression of the earth around them, so the cover of the tube would naturally be round as well 6 It’s easier to dig a circular hole
