[单选题]
A proton, initially 2t3makfd q-af + s2.xi. kgwuu7ib+ hcjv );k249f asnat rest, is accelerated through an electric potential difference of 500 V. kn;k2b gwiu79f c s 4vja)uh.+What is the speed of the proton?
A. $2.2 \times 10^{5} \; m/s$
B. $3.1 \times 10^{5} \; m/s$
C. $9.6 \times 10^{10} \; m/s$
D. zero
