Transaction-related audit objectives are essentially the same for processing credit memos as for sales with certain differences. Which of the following are two key differences?

Transaction-related audit objectives are essentially the same for processing credit memos as for sales with certain differences. Which of the following are two key differences?

    a.    Risk and emphasis on the completeness objective.
    b.    Materiality and emphasis on the accuracy objective.
    c.    Risk and emphasis on the classification objective.
    d.    Materiality and emphasis on the occurrence objective.