After obtaining an understanding of internal control and assessing control risk, an auditor decided to perform test of controls. The auditor most likely decided that: 

• a. An increase in the assessed level of control risk is justified for certain financial statement assertions. 
• b. There were many internal control weaknesses that could allow errors to enter the accounting system. 
• c. It would be efficient to perform test of controls that would result in a reduction in planned substantive tests. 
• d. Additional evidence to support a further reduction in control risk is not available.