The straight long conductors AOB and COD are perpendicular to each other and carry current `i_(1)` and `i_(2)`. The magnitude of the magnetic induction at point P at a distance a from the point O in a direction perpendicular to the plane ACBD is
A. `(mu_(0))/(2pia)(i_(1)+i_(2))`
B. `(mu_(0))/(2pia)(i_(1)-i_(2))`
C. `(mu_(0))/(2pia)(l_(1)^(2)+i_(2)^(2))^(1//2)`
D. `(mu_(0))/(2pia)(i_(1)i_(2))/(i_(1)+i_(2))`