The quantity \( (p_0 g q)^{1/2} \) represents the speed of light \( c \) in CGS units, which is approximately:
\[
c = 3 \times 10^{10} \, \text{cm/s}.
\]
Given that option (A) is \( 3 \times 10^{8} \, \text{cm/s} \), which equals \( 3 \times 10^{6} \, \text{m/s} \), this appears to be a typo or error in the units.
The correct value for the speed of light in CGS units is closer to \( 3 \times 10^{10} \, \text{cm/s} \), thus option (B) is intended to represent this value.