Final answer:
A CPA client filing suit for negligence in performing an audit pertains to Common law, since the Securities Acts of 1933 and 1934 do not address auditor negligence directly.
Step-by-step explanation:
If a CPA (Certified Public Accountant) client is filing suit for negligence in the performance of an audit, the relevant area of law would typically be Common law. The Securities Act of 1933 and the Securities Exchange Act of 1934 are federal securities laws that govern the issuance and trading of securities, but they do not directly address professional negligence in auditing. Instead, a negligence claim against a CPA for an audit generally arises under the Common law principles of professional malpractice, which would involve proving the CPA had a duty to the client, breached that duty, and as a result of the breach, the client suffered damages.