[单选题]
Estimate the speed of an alpha part+d 27vd bqe5qv/jf7myicle that has accelerated fk+v:s e)rtx. ng 9+ytprom rest in a uniform electric fi+.:rv tpgtkns) 9+xeyeld E=50 $^{−1}$ over a distance of 2.0m.
A. $0.5\times10^4\,ms^{−1}$
B. $5.0\times10^4\,ms^{−1}$
C. $0.5\times10^5\,ms^{−1}$
D. $0.5\times10^9\,ms^{−1}$
