解:两种方案都可行。理由:琪琪的方案:
在$\triangle AOB$和$\triangle COD$中
$\begin {cases}AO = CO\\∠AOB = ∠COD\\BO = DO\end {cases}$
∴$\triangle AOB≌\triangle COD(S AS),$∴$AB = CD$
嘉嘉的方案:在$Rt\triangle ABD$和$Rt\triangle CBD$中
$\begin {cases}AD = CD\\BD = BD\end {cases}$
∴$Rt\triangle ABD ≌ Rt\triangle CBD(\mathrm {HL}),$∴$AB = BC$