$h=6,{{625.10}^{-34}}\,\,\left( Js \right)$
$f=3,{{2.10}^{18}}\,\,\,\left( Hz \right)$
$e=1,{{6.10}^{-19}}\,\,\,\left( C \right)$
…………………………………………….
$A=h.f=U.q$
$\to h.f=U.e$
$\to U=\dfrac{h.f}{e}$
$\to U=\dfrac{6,{{625.10}^{-34}}.3,{{2.10}^{18}}}{1,{{6.10}^{-19}}}$
$\to U=13250\,\,\,\left( V \right)$
$\to U=13,25\,\,\,\left( kV \right)$
$\to $ câu $D$