The reduction potential of hydrogen half cell will be negative if $(T=298 K )$ :
(A) $P_{ H _{2}}=1 atm$ and $\left[ H ^{+}\right]=1.0 M$
(B) $P_{ H _{2}}=2 atm$ and $\left[ H ^{+}\right]=2.0 M$
(C) $P _{ H _{2}}=2 atm$ and $\left[ H ^{+}\right]=1.0 M$
(D) $P_{ H _{2}}=1 atm$ and $\left[ H ^{+}\right]=2.0 M$