# The thermo emf of a thermocouple varies with the temperature $\theta$ of the hot junction as $E= a \theta + b \theta^2$ in volts where the ratio $a/b$ is $700^{\circ}C$. If the cold junction is kept at $0^{\circ}C$, then the neutral temperature is
( A ) $700^{\circ}C$
( B ) $1400^{\circ}C$
( D ) $350^{\circ}C$