The thermo emf of thermocouple varies with the temperature `theta` of the hot junction as `E = atheta + btheta^2` in volts where the ratio `a//b` is `700^@C`. If the cold junction is kept at `0^@C`, then the neutral temperature is
A. `700^(@)C`
B. `350^(@)C`
C. `1400^(@)C`
D. No neutral temperature is possible for this