Why is the answer (A)?
In details please​

Explanation:

resistance of wire can be determined by this equation

R = Rho . L / A

L = the length of wire

A = the Area, A = πr²

Rho = density of resictance

we can do some rational

R1/R2 = ( Rho L1/A1) / (Rho L2/A2)

L2 is the condition when the length is doubled and

L2 = 2 x L

A2 is the condition when the diameter is doubled

A2 = 4A1

R/R2 = (L1/A1)/(L2/A2)

R/R2 = (L/A) / (2L/4A)

R/R2 = 1 / ½

R2 = ½ R.

then we use formula of Voltage

V = I R

1st condition

V = 0.3 R

2nd condition ( V is constant)

V = I2 R2

0.3 R = I2 x ½R

i2 = 0.3/ ½

i2 = 0.6 Ampere