If 1 is added to each odd digit and 2 is subtracted from each even digit in the number 7735821, what will be difference between the highest and lowest digits in the new number thus formed?

Given: ​7735821

Add 1 to each odd digit and subtract 2 from each even digit.

7 (odd) → 7 + 1 = 8

7 (odd) → 7 + 1 = 8

3 (odd) → 3 + 1 = 4

5 (odd) → 5 + 1 = 6

8 (even) → 8 − 2 = 6

2 (even) → 2 − 2 = 0

1 (odd) → 1 + 1 = 2

New number: 8, 8, 4, 6, 6, 0, 2

The difference between the highest and lowest digit:

Highest = 8

Lowest = 0

Difference = 8 - 0 = 8

So, 8 will be difference between the highest and lowest digits in the new number thus formed.

Thus, correct option is (c).