Final answer:
Every audit involves (Option 3) some amount of substantive testing as required by audit standards for relevant assertions. Substantive testing is used to obtain sufficient audit evidence for the financial statements. The process is somewhat similar to confirming the existence of a tangible item, like milk in a refrigerator, through verification.
Step-by-step explanation:
Every audit will involve some amount of substantive testing because audit standards require it for relevant assertions. This is because substantive testing is a key component in obtaining audit evidence to reach a conclusion on the fairness of the financial statements. Typically, auditors use a combination of substantive testing and other audit procedures to assess the reliability of financial information provided by a company. Substantive testing may include verification of transactions, balances, and disclosures.