Correct option is D one-ninth the resistance of ammeter
Full scale deflection voltage be V
Now initiall range is I
$$
\mathrm{V}=\mathrm{IR}
$$
Now, Range is made $10 \mathrm{I}$
$$
\begin{array}{l}
\mathrm{V}=10 \mathrm{IR}^{\prime} \\
\mathrm{R}^{\prime}=\mathrm{V} / 10 \mathrm{I}=\mathrm{R} / 10
\end{array}
$$
therefore, newR $_{\underline{o q}}$ of parallel combination will be $\mathrm{R} / 10$ therefore,
$$
\begin{array}{l}
1 / R_{e q}=1 / R+1 / R_{p} \\
1 / R_{p}=1 / R_{e q}-1 / R=10 / R-1 / R=9 / R
\end{array}
$$
therefore, $\mathrm{R}_{\mathrm{p}}=\mathrm{R} / 9$ option(D)