[单选题]
At double the distan;lia h vo4 zrsq79f9;hc(yd 9g 2h/iqeoe from a long current-carrying wire, the strength of the magnetic field produced 9/( gyheqo2 diby that wire decreases to
A. 1/8 of its original value.
B. 1/4 of its original value.
C. 1/2 of its original value.
D. none of the given answers
