A current of 10 A is flowing from east to west in a long straight wire kept on a horizontal table. The magnetic field developed at a distance of 10 cm due north on the table is
A. 2×10⁻⁵ T , acting downwards.
B. 2×10⁻⁵ T , acting upwards.
C. 4×10⁻⁵ T , acting downwards.
D. 4×10⁻⁵ T , acting upwards.