Which of the following statements regarding internal controls is most true?

a. Assessing the control environment is important because management can override control activities

b. If internal controls are assessed as weak and the auditor does not seek to place reliance on them, some controls testing is still required

c. Internal control risk is determined at the account balance level and detection risk is determined at the assertion level

d. If internal controls are very strong, no substantive testing is required by the auditor