Wires A as well as wire B are both made out of copper. Both of wires have the same length. The diameter of wire B is doubles that of wire A.

Answer:

Resistivity is a characteristic of the material. It doesn't depend on the size and shape of the object. (The object is a piece of wire in each case.) As both wires are made of copper the resistivity is the same for both wires.

The skinnier wire proposes the smaller passageway for charged particles to flow through. As such it proposes more resistance to the flow of charge. In other sense the resistance of the skinnier wire is greater than that of the fatter wire.