In which of the following circumstances is it most likely that a CPA has violated the Code of Professional Conduct?

Multiple Choice

He serves as trustee of an audit client's profit$-$sharing trust.

He has placed an ad in a newspaper in which he compares his audit firm personnel's experience with that of the personnel of several competing firms.

He audits a company in which he previously owned stock.

He has started an audit of a nonissuer $($nonpublic company$)$ for which last year's fees have not yet been received.