The ease of adsorption of the hydrated alkali metal ions on ion-exchange resins follows the order:
(a)`K^(+) lt Na^(+) lt Rb^(+) lt Li^(+)`
(b)`Na^(+) lt Li^(+) lt K^(+) lt Rb^(+)`
(c)`Li^(+) lt K^(+) lt Na^(+) lt Rb^(+)`
(d)`Rb^(+) lt K^(+) lt Na^(+) lt Li^(+)`

Options

A. `K^(+) lt Na^(+) lt Rb^(+) lt Li^(+)`
B. `Na^(+) lt Li^(+) lt K^(+) lt Rb^(+)`
C. `Li^(+) lt K^(+) lt Na^(+) lt Rb^(+)`
D. `Rb^(+) lt K^(+) lt Na^(+) lt Li^(+)`

Explanation

To solve the question regarding the ease of adsorption of hydrated alkali metal ions on ion-exchange resins, we need to analyze the factors that influence this process.

### Step-by-Step Solution:

1. **Understanding Ion Size**: The ease of adsorption of ions on ion-exchange resins is primarily influenced by the size of the ions. Smaller ions tend to be adsorbed more easily than larger ions.

2. **Trends in Alkali Metal Ions**: Alkali metal ions (Li⁺, Na⁺, K⁺, Rb⁺) increase in size as we move down the group in the periodic table. Therefore, Li⁺ is the smallest, followed by Na⁺, K⁺, and Rb⁺, which is the largest.

3. **Effect of Size on Adsorption**: As the size of the ion increases, the ease of adsorption decreases. This means that the smaller the ion, the easier it is for it to be adsorbed onto the ion-exchange resin.

4. **Order of Ease of Adsorption**: Based on the size of the ions, we can establish the order of ease of adsorption:
- Li⁺ (smallest) > Na⁺ > K⁺ > Rb⁺ (largest)

5. **Conclusion**: Therefore, the correct order of ease of adsorption of the hydrated alkali metal ions on ion-exchange resins is:
- **Li⁺ > Na⁺ > K⁺ > Rb⁺**

6. **Selecting the Correct Option**: The correct option that reflects this order is:
- (d) Rb⁺ < K⁺ < Na⁺ < Li⁺

### Final Answer:
The correct answer is (d) Rb⁺ < K⁺ < Na⁺ < Li⁺.