18. A wire is 1 m long and 1 x 106 m² in cross-sectional area. When connected to a potential difference of 2 V, a current of 4 A exists in the wire. The resistivity of this wire is: A) 2 × 106 2-m B) 8 × 106 2-m C) 1 x 10-72-m D) 4 × 107 2-m E) 5 × 107 2.m