Step 1: Use the relation between Young's modulus and shear modulus.
\[
E=2G(1+\mu).
\]
Hence,
\[
G=\frac{E}{2(1+\mu)}.
\]
Step 2: Substitute the given values.
Given,
\[
E=60\ \text{MPa},
\qquad
\mu=0.3.
\]
Therefore,
\[
G
=
\frac{60}{2(1.3)}
=
\frac{60}{2.6}
=
23.08\ \text{MPa}.
\]
Thus,
\[
\boxed{G\approx23\ \text{MPa}.}
\]
Hence,
\[
\boxed{(C)}
\]
is the correct answer.