[单选题]
A cyclotron of radius 03muxnx 7 b(k2d 2bfhe0.25 m accelerates protons c0xz5 u7lt lk4qm2 at.in a 1.7-T magnetic field. What is the frequency for the aq7 auxmz2 kc.0 4t5tllpplied alternating voltage?
A. $0.26 \; MHz$
B. $2.6 \; MHz$
C. $26 \; MHz$
D. $260 \; MHz$