Three wires, A, B and C, of the same length and the same thickness have resistances of 1 Ω, 0.5 Ω and 0.25 Ω, respectively. Their resistivities are ________ .
1
In the ratio of 4 ∶ 2 ∶ 1
2
in the ratio of 1 ∶ 2 ∶ 4
3
in the ratio of 2 ∶ 4 ∶ 1
4
equal