NO$\mathrm{.}242$ A finance department has a multi$-$year project to upgrade the enterprise resource planning $($ERP$)$ system hosting the general ledger. and in year one, the system version upgrade will be applied. Which of the following should be the PRIMARY focus of the IS auditor reviewing the first year of the project?$($A$).$ unit testing$($B$).$ Network performance$($C$).$ User acceptance testing $($UAT$)($D$).$ Regression testing