[单选题]
A cyclotron of radius 0.25 m accel po uko /p0rgoda8735perates protons in a 1.74jcr4 khok**:p:uzxlaec *8 m-T magnetic field. What is the freq*ha4 r::ccul8 xp* kjo*4kemzuency for the applied alternating voltage?
A. $0.26 \; MHz$
B. $2.6 \; MHz$
C. $26 \; MHz$
D. $260 \; MHz$
