如图，已知 $\mathit{\Delta ABC}\backsim \mathit{\Delta DEF}$， $\mathit{AB}:\mathit{DE}=1:2$，则下列等式一定成立的是 $($　　 $)$

A． $\frac{\mathit{BC}}{\mathit{DF}}=\frac{1}{2}$B． $\frac{\angle A\mathit{的度数}}{\angle D\mathit{的度数}}=\frac{1}{2}$

C． $\frac{\mathit{\Delta ABC}\mathit{的面积}}{\mathit{\Delta DEF}\mathit{的面积}}=\frac{1}{2}$D． $\frac{\mathit{\Delta ABC}\mathit{的周长}}{\mathit{\Delta DEF}\mathit{的周长}}=\frac{1}{2}$