The unit of electric current "ampere" is the current which when flowing through each of two parallel wires spaced `1 m` apart in vacuum and of infinite length will give rise to a force between them equal to
A. `1N//m`
B. `2xx10^(-7)N//m`
C. `1xx10^(-2)N//m`
D. `4pi xx10^(-7)N//m`
