In a Delta Modulation (DM) system, A sinusoidal test signal of amplitude Am=1(V) and frequency fm = 1 (kHz) is applied to the system. The sampling rate is fs = 8 (kHz) ，to avoid slope overload, the step size Δ is at least (V).
A、0.125
B、0.785
C、1.57
D、0.3925

A.

B.125
C.785
D.57
E.3925