1. Bohr’s angular momentum quantization

   According to Bohr’s theory, the angular momentum of an electron in the $n^{\text{th}}$ orbit is: $L = n\frac{h}{2\pi}$

2. For the $4^{\text{th}}$ orbit

   Here, $n=4$. So, $L = 4\frac{h}{2\pi} = \frac{4h}{2\pi} = \frac{2h}{\pi}$

3. Match with the options

   • A: $2\frac{h}{\pi}$ ✅
   • B: $\frac{h}{2\pi}$
   • C: $\frac{h}{\pi}$
   • D: $8\frac{h}{\pi}$

Therefore, the correct answer is Option A.