Choice "D" is correct. Deviations from control activities do not necessarily result in misstatements. Therefore, deviations from pertinent control activities at a given rate would ordinarily be expected to result in misstatements at a lower rate.
Choice "b" is incorrect. In tests of controls, population size has virtually no effect on sample size unless the population is small.
Choice "a" is incorrect. There is a direct relationship between expected deviation rate and sample size.
Choice "c" is incorrect. Detection risk and sample size are not factors in determining the tolerable deviation rate in a test of controls. The tolerable rate is simply the maximum rate that the auditor is willing to accept without altering his or her planned level of reliance.