`{:(Column I,Column II),((A)"Radius of" n^(th) "orbit",(p)"Inversely proportional to Z"),((B)"Energy of" n^(th)"orbit",(q)"Integral multiple of"(h)/(2pi)),((C)"Velocity of electron" " in " n^(th) "orbit",(r)"Proportional to n^(2)"),((D)"Angular momentum",(s)"Inversely proportional to n"),(,(t)"Inversely proportional too" n^(2)):}`

Explanation

To solve the question, we need to match the items from Column I with the correct descriptions in Column II based on the principles of Bohr's model of the atom.

### Step-by-Step Solution:

1. **Radius of n-th Orbit (A)**:
- According to Bohr's model, the radius of the n-th orbit is given by the formula:
\[ r_n = \frac{r_0 n^2}{Z} \]
- Here, \( r_0 \) is a constant (approximately 0.53 Å), \( n \) is the principal quantum number, and \( Z \) is the atomic number.
- From this formula, we can see that the radius is **inversely proportional to Z** and **proportional to \( n^2 \)**.
- **Match**: A matches with P (Inversely proportional to Z) and R (Proportional to \( n^2 \)).

2. **Energy of n-th Orbit (B)**:
- The energy of the electron in the n-th orbit is given by:
\[ E_n = -\frac{13.6 Z^2}{n^2} \text{ eV} \]
- This indicates that the energy is **inversely proportional to \( n^2 \)**.
- **Match**: B matches with T (Inversely proportional to \( n^2 \)).

3. **Velocity of Electron in n-th Orbit (C)**:
- The velocity of the electron in the n-th orbit is given by:
\[ v_n = v_0 \frac{Z}{n} \]
- Here, \( v_0 \) is a constant. This shows that the velocity is **inversely proportional to n**.
- **Match**: C matches with S (Inversely proportional to n).

4. **Angular Momentum (D)**:
- According to Bohr's model, the angular momentum of the electron is quantized and given by:
\[ L = mvr = n\frac{h}{2\pi} \]
- This indicates that angular momentum is an **integral multiple of \( \frac{h}{2\pi} \)**.
- **Match**: D matches with Q (Integral multiple of \( \frac{h}{2\pi} \)).

### Final Matches:
- A → P, R
- B → T
- C → S
- D → Q