Consider \[\alpha \] particles, \[\beta \] particles and \[\gamma \] - rays, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are:

• A. \[\alpha ,\,\,\beta ,\,\,\gamma \]
• B. \[\alpha ,\,\,\beta ,\,\,\gamma \]
• C. \[\beta ,\,\,\gamma ,\,\,\alpha \]
• D. \[\gamma ,\,\,\beta ,\,\,\alpha \]