Choice "B" is correct. There is an inverse relationship between the tolerable deviation rate and sample size: as the auditor is willing to accept a greater deviation rate, a smaller sample size can be used.
Choice "a" is incorrect. There is a direct relationship between expected deviation rate and sample size: as the likely rate of deviation decreases, a smaller sample size can be used.
Choice "d" is incorrect. There is an inverse relationship between the risk of assessing control risk too low and sample size: as the allowable level of risk increases, the sample size decreases.
Choice "c" is incorrect. Population size has a relatively small effect on sample size, especially in large populations.