The wave length of an probe is volubly a measure of the size of a structure that it can probe in some detail. The quark structure of protons and neutrons appear at the last minute length - scale of $10^{-5}\;m$ or less. This structure was first probed in early 1970's using high energy electron beam produced by a linear acceleration at stanford USA. guess what might have been the order of energy of these electron beams . (Rest mass energy of electron $=0.511\; Mev$)

Question

$\begin{array}{1 1} \text{The electron energies from the accelerator must been few Kev} \\ \text{The electron energies from the accelerator must been few Mev} \\ \text{The electron energies from the accelerator must been few Bev} \\ \text{The electron energies from the accelerator must been few Gev} \end{array} $