Sue and Andy are discussing internal control with a new audit intern, Mark. Mark has heard about the importance of internal control from his professor; however he still fails to see why internal control is important. Which of the following represent Sue and Andy's best response to this question?

Group of answer choices

a.Internal control is designed and implemented by the client, and helps to prevent and detect misstatements in the firm's financial statements.

b.None of these answer choices are correct.

c.Internal control is required to be implemented by all companies, and is designed to ensure that no misstatements whatsoever exist in the firm's financial statements.

d.Internal control is optional for larger companies, as their processes and operations are usually efficient enough to where this type of system is not needed.