Consider two thin identical conducting wires covered with very thin insulating material.One of the wires is bent into a loop and produces magnetic field `B_(1)` at its centre when a current I passes through it.The second wire is bent into a coil with three identical loops adjacent to each other and produces magnetic field `B_(2)` at the centre of the loops when current "I/3" passes through it.The ratio `B_(1):B_(2)` is: (a) 1:3 (b) 9:1 (c) 1:9 (d) 1:1