How does $\backslash (\backslash$S $10\mathrm{.}2\backslash )$ of Circular $230$ define "Practice before the IRS"?

Select one:a$.$ Performing any act that requires a tax preparer's licenseb. Direct written, electronic, or in$-$person communication with the IRSc. Any act involved in tax preparation or advocacy for a clientd. Appearing in person before a reviewer or auditor employed by the IRS