The thermo e.m.f. of a thermocouple is `25 uV//"^@C` at room temperature. A galvanometer of `40 Omega` resistance, capable of detecting current as low as `10^-5A`, is connected with the thermocouple. The smallest temperature difference that can be detected is

Options

A. `20^@C`
B. `16^@C`
C. `12^@C`
D. `8^@C`.