re > rp > rHe
re < rp = rHe
re < rp < rHe
re > rp = rHe
Correct option is C. re < rp < rHe
r = mv/qB = 2mK/qB
For same energy K, r is proportional to m/q.
rHe/rp = (mHe/mp) * (qp/qHe) = (4/1)(1/2) = 2
rHe = 2rp
re/rp = (me/mp) * (qp/qe) = (1/1836)(1/1) ≈ 0.0005
re << rp
Therefore, re < rp < rHe