Step 1:Write the relation for ripple frequency.
\[
f_r=2f
\]
where
\[
f_r=\text{ripple frequency}
\]
and
\[
f=\text{input AC frequency}
\]
Step 2: Substitute the given frequency.
Given,
\[
f=50\,\text{Hz}
\]
Therefore,
\[
f_r=2\times50
\]
\[
f_r=100\,\text{Hz}
\]
Step 3: State the answer.
\[
{
f_r=100\,\text{Hz}
}
\]
Hence, the correct option is
\[
{(D)}
\]