When auditing financial statements of a private company, the minimum work an auditor must perform in connection with a company's internal control is best described by which of the following statements:
a. Perform exhaustive tests of accounting controls and evaluate the company's control system effectiveness
b. Determine whether the company's control policies are designed well enough to prevent material errors
c. Prepare auditing working papers documenting the understanding of the company's internal control
d. Design procedures to search for significant deficiencies in the actual operation of the company's internal control