Correct Answer - Option 4 :
\(\frac{{1 - {e^{ - Ts}}}}{s}\)
The impulse response of the zero-order hold is shown below.
From the above response, g(t) = u(t) – u(t – T)
By applying the Laplace transform,
\(G\left( s \right) = \frac{1}{s} - \frac{{{e^{ - Ts}}}}{s}\)
\(=\frac{{1 - {e^{ - Ts}}}}{s}\)