The Temperature Coefficient of Resistivity of Iron Is 5

Multiple Choice

The temperature coefficient of resistivity of iron is 5.0 × 10⁻³ / °C; that of carbon is −0.50 × 10⁻³ / °C. When an iron wire and a carbon rod, each having the same 10-Ω resistance at 20°C, are cooled from that temperature to −80°C, the new ratio of the resistance of the carbon rod to the resistance of the iron wire at the lower temperature is

A) −0.10.
B) +1.9.
C) +2.1.
D) −10.
E) +10.