已知全集$U=\left\{1,2,3,4,5\right\}$，集合$A=\left\{1,2\right\}$，$B=\left\{2,3,4\right\}$，则$B\cap C_{U}A$=

$\left\{2\right\}$ $\left\{3,4\right\}$ $\left\{1,4,5\right\}$ $\left\{2,3,45\right\}$