单项选择题
信号f(t)=ε(t)*(δ(t)-δ(t-4))的单边拉氏变换F(S)=()
A.A B.B C.C D.D
A.Rs、RL、R均加大 B.Rs、R减小,RL加大 C.Rs、RL、R均减小 D.Rs、RL加大,R减小