[单选题]
A cyclotron operates ac w*xkk/di 6po;6z8id:*l fae ki;8 *y)qulsat 10 MHz. What magnetic field is needeo c3phi w(-jrsgp+50;v d8b mk+;bevvd to accelerate protonigskwcrpo;j ;8- 3bev+vphv( 5m0b+ds?
A. $0.12 \; T$
B. $0.25 \; T$
C. $0.66 \; T$
D. $1.5 \; T$
