Choice "B" is correct. If the actual deviation rate in the population exceeds the maximum deviation rate based on the sample, control risk will be understated, since the control will be less effective than sample results would indicate.
Choice "c" is incorrect. No comparison should be made between the true deviation rate and the risk of assessing control risk too low.
Choice "a" is incorrect. If the true deviation rate is lower than the deviation rate in the sample, control risk may be assessed at a rate that is too high, potentially leading to audit inefficiencies.
Choice "d" is incorrect. No comparison should be made between the true deviation rate and the risk of assessing control risk too low.