A prefect gas is found to obey the relation $P V^{3 / 2}=$ constant during an adiabatic process. if such a gas initially at a temperature $T$, is compressed to half of its initial volume, then its final temperature will be
(a) $2 T$
(b) $4 T$
(c) $(2)^{1 / 2} T$
(d) $2(2)^{1 / 2} T$