When a unit step voltage drives a lag network the output

[A].	remains constant at unit step value
[B].	increases exponentially from zero to final value
[C].	decreases exponentially from 1 to 0
[D].	either (b) of (c) depending on values of R and C

Answer: Option B

Explanation:

At t = 0 the capacitor behaves as a short-circuit and output voltage is 0. At t = ∞ capacitor behaves as an open-circuit and V0 = Vi.