Choice "C" is correct. Failure to record sales returns would result in actual inventory quantities being greater than those recorded in the perpetual inventory records.
Choice "d" is incorrect. Failure to record purchase discounts would result in a difference in recorded costs, rather than recorded quantities.
Choice "b" is incorrect. Failure to record purchase returns would result in actual inventory quantities being less than those recorded in the perpetual inventory records.
Choice "a" is incorrect. Failure to record sales would result in actual inventory quantities being less than those recorded in the perpetual inventory records.