[单选题]
A proton has a speed mb,8/ v6i bdpqolj 2i 9lxmk:n8f $3.0 \times 10^6 \; m/s$ in a direction perpendicular to a uniform magnetic field, and the proton moves in a circle of radius 0.20 m. What is the magnitude of the magnetic field?
A. $0.080 \; T$
B. $0.16 \; T$
C. $0.24 \; T$
D. $0.32 \; T$
