Which of the following statements is an advantage of classical variables sampling?

a. If no errors are expected, classical variables sampling will result in a smaller sample size than probability-proportional-to-size sampling.

b. A classical variables sampling plan can begin before the completed population is available.

c. Classical variables sampling may result in a smaller sample size than probability proportional- to-size sampling if there are many differences between recorded and audited amounts.

d. Classical variables sampling does not require recorded values for individual sampling units.

Choose the correct answer.