Two long parallel wires are at a distance of 1m. If both of them carry one ampere of current in same direction, then the force of attraction on unit length of the wires will be
A. 2×10⁻⁷N/m
B. 8×10⁻⁷N/m
C. 10⁻⁷N/m
D. 4×10⁻⁷N/m