Vera Is Audited by the IRS for Three Tax Years

Vera is audited by the IRS for three tax years. Her returns were prepared by the following parties, to each of whom Vera paid a professional fee.
Vera wants help in appearing before the IRS Revenue Agent for the audit. Which of the following statements is correct?

A) Sally may represent Vera for all tax years involved.
B) Wesley may represent Vera, but only for tax year 2.
C) Alex can represent Vera, but only for tax year 3.
D) Vera may represent herself for all tax years involved.