Why Do Auditors Generally Use a Sampling Approach to Evidence

Why do auditors generally use a sampling approach to evidence gathering?

A) Auditors are experts and do not need to look at much to know whether the financial statements are correct or not.
B) Auditors must balance the cost of the audit with the need for precision.
C) Auditors must limit their exposure to their client to maintain independence.
D) The auditor's relationship with the client is generally adversarial, so the auditor will not have access to all of the financial information of the company.