Explanation:

- Ujjwal's downstream speed is 50 km in 2 hours, so 25 km/h.

- Ujjwal's upstream speed is 28 km in 4 hours, so 7 km/h.

- Speed in still water can be calculated from average of upstream and downstream speeds: (25 + 7) / 2 = 16 km/h.

- To determine the time to cover 32 km in still water:

$$ \text{Time} = \frac{\text{Distance}}{\text{Speed}} = \frac{32 \text{ km}}{16 \text{ km/h}} = 2 \text{ hours} $$

- Option:1 - 2 hours (Correct Answer)

- Option: 2.5 hours (Not correct)

- Option: 1.5 hours (Not correct)

- Option: 3 hours (Not correct)

- Option: None of these (Not correct)