Which change decreases the resistance of a piece

of copper wire?

(1) increasing the wire's length

(2) increasing the wire's resistivity

(3) decreasing the wire's temperature

(4) decreasing the wire's diameter

The resistance of a wire is given by: Resistance = (resistivity x length) / (cross sectional area). Resistivity is a property specific to a substance and it increases with increased temperature. Therefore, if we want to increase resistance, the best way would be to increase the wire's length.