Which of the Following Would Best Be Described as an Assurance

Which of the following would best be described as an assurance service?

A) Preparing a report representing a client's position during an IRS audit.
B) Working with a client to develop a more efficient method of processing financial transactions.
C) Offering an opinion concerning the accuracy of statements made on a client's website relating to the client's online privacy policies.
D) Assisting a client in identifying potential sources of capital for potential acquisitions.