图中系统的连续传递函数为(G(s)=dfrac{K}{(s+1)(s+2)},,,,,F(s)=1)则闭环系统的脉冲传递函数为
A
A.(dfrac{Kz({rm e}^{-T}+{rm e}^{-2T})}{(z+{rm e}^{-T})(z+{rm e}^{-2T})+Kz({rm e}^{-T}+{rm e}^{-2T})})
B
B.(dfrac{Kz({rm e}^{-T}+{rm e}^{-2T})}{(z-{rm e}^{-T})(z-{rm e}^{-2T})+Kz({rm e}^{-T}+{rm e}^{-2T})})
C
C.(dfrac{Kz({rm e}^{-T}-{rm e}^{-2T})}{(z-{rm e}^{-T})(z-{rm e}^{-2T})+Kz({rm e}^{-T}-{rm e}^{-2T})})
