[单选题]
A cyclotron operates at 10 MHz. What magnetic field is needed tx35p2 hcgau4h )xwxu*4 pn ,gw0ctf2ro accelerat0k61iqn 40 9awctuuj5ob( ,vf o ,yiule protons , 9i ,0tvqunoubic( a0lk41j65wuf oy?
A. $0.12 \; T$
B. $0.25 \; T$
C. $0.66 \; T$
D. $1.5 \; T$