Step 1: Apply the Nyquist stability criterion.
According to the Nyquist criterion,
\[
Z=P-N,
\]
where
\[
\begin{aligned}
P &= \text{Number of open-loop RHP poles},
N &= \text{Net clockwise encirclements of }(-1,0),
Z &= \text{Number of closed-loop RHP poles}.
\end{aligned}
\]
Step 2: Substitute the given values.
Given,
\[
P=1,
\]
and the Nyquist plot encircles \((-1,0)\) twice clockwise, so
\[
N=-2.
\]
Therefore,
\[
Z=P-N
=1-(-2)
=3.
\]
Hence,
\[
\boxed{Z=3.}
\]
Therefore,
\[
\boxed{(D)}
\]
is the correct answer.