[单选题]
A cyclotron of radius 0.25 m accelerates protons in a 1.7-T msh.wir u q/5l5 mk;cn0agnetic fieldurhd0kyr(iy)b g9m 5w*h ,*ne . What is the frequency for the applikryrmb)9dh*wg*eh0 ui( ,ny5 ed alternating voltage?
A. $0.26 \; MHz$
B. $2.6 \; MHz$
C. $26 \; MHz$
D. $260 \; MHz$
