Explanation

(c) According to Bohr’s theory of atom electrons can revolve only in those orbits in which their angular momentum is an integral multiple of$\frac{h}{2\pi}$, where $h$ is Planck’s constant.
Angular momentum = $mvr$=$\frac{2h}{2\pi}$
Hence, angular momentum is quantized.
The energy of electron in $n$th orbit of hydrogen atom,
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E\ =$ $\frac{Rhc}{n^{2}}$ joule
Thus, it is obvious that the hydrogen atom has some characteristics energy state. In fact this is true for the atom of each element, $ie,$ each atom has its energy quantized.
Hence, both energy and angular momentum are quantised.