Which of the following best describes the relationship between auditing and attestation engagements?

a. Auditing is a subset of attestation engagements that focuses on the certification of financial statements.

b. Attestation is a subset of auditing that provides lower assurance than that provided by an audit engagement.

c. Auditing is a subset of attestation engagements that focuses on providing clients with advice and decision support.

d. Attestation is a subset of auditing that improves the quality of information or its context for decision makers.