The impulse response of a second-order system for the transfer function H(s) = ω₀² is represented by:
a) h(t) = δ(t)
b) h(t) = 2δ(t)
c) h(t) = e(-ω₀t)u(t)
d) h(t) = ω₀e(-ω₀t)u(t)