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

1. -0.10.
2.+;2.1.
3. -10.
4. +;1.9.
5.+;10.