Electrons are accelerated in television tubes through potential differences of about 10 kV. The highest frequency of the electromagnetic waves emitted when these electrons strike the screen of the tube is

• A

  $2.4\times {10}^{18}\mathrm{Hz}$

• B

  $3.6\times {10}^{18}\mathrm{Hz}$

• C

  $2.2\times {10}^{17}\mathrm{Hz}$

• D

  $3.2\times {10}^{16}\mathrm{Hz}$