[单选题]
What is the magnetic field at the center of a circular loop ofg0nljji 3i9e8j*pm b4 wire k5i-m pte6)wzof radius 4.0 cm when a current of 2.0 A flows ize 65m kwp-ti)n the wire?
A. $1.3 \times 10^{-6} \; T$
B. $3.1 \times 10^{-6} \; T$
C. $1.3 \times 10^{-5} \; T$
D. $3.1 \times 10^{-5} \; T$
