According to Bohr's theory E_n= Total energy, K_n= Kinetic energy,...

According to Bohr's theory, Total energy is $E_n=K_n+V_n$ Kinetic energy $=K_n=\frac{1}{8 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}$ Potential energy $=V_n=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}\therefore \quad E_n=\frac{1}{8 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}-\frac{1}{4 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}$ Radius of $n$th orbit \left(r_n\right)=\frac{n^2 h^2 \varepsilon_0}{\pi m Z e^2}$E_n=-$\frac{m e^4}{8 \varepsilon_0^2 h^2} \times \frac{1}{n^2} ($A)$\frac{V_n}{K_n}=\frac{-\frac{1}{4 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}}{\frac{1}{8 \pi \varepsilon_0} \cdot \frac{Z e^2}{r}}=-2$Hence,$(A)$match with$(R)$. (B)$E_n \propto \frac{1}{n^2}$or$E_n \propto \frac{1}{r_n}$Radius of$n$th orbit$r_n \propto E_n^x\therefore \quad x=-1Hence, (B) match$with (Q). (C) Angular momentum =$\frac{h}{2 \pi}$\sqrt{l(l+1) l}=0,1,2, \ldots$ For the lower orbit $n=1\therefore \quad l=0 and m=0 Hence, angular momentum of$lowest orbit =\frac{h}{2 \pi} \sqrt{0(0 H)}=0$(C) match with (P) (D)$\frac{1}{r^n} \propto Z^y$as$r_n \propto \frac{1}{Z} \therefore y=1 Hence, (D) match with (S).