(b)
$CH_{3}CH_{2}C \equiv CH\underset{\mathrm{\Delta}}{\overset{\frac{Na}{Liq.{NH}_{3}}}{\rightarrow}}CH_{3}CH_{2}C \equiv CNa^{+}$
Considering the options given it appears correct. $\frac{Na}{liq.{NH}_{3}}$ is known for metal dissolved reduction. Actually it is truth that $\frac{Na}{liq.{NH}_{3}}$ reduces internal triple bond and terminal double bond and do not reduce the terminal alkyne due to such alkylide formation.