If 1 is added to each odd digit and 1 is subtracted from each even digit in the number 1865374, which of the following digits will be third from the left in the new number thus formed?

Given: 1865374

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

1 (odd) → 1 + 1 = 2

8 (even) → 8 − 1 = 7

6 (even) → 6 − 1 = 5

5 (odd) → 5 + 1 = 6

3 (odd) → 3 + 1 = 4

7 (odd) → 7 + 1 = 8

4 (even) → 4 − 1 = 3

New number: 2, 7, 5, 6, 4, 8, 3

Third from left = 5

So, 5 will be third from the left in the new number thus formed.

Thus, correct option is (c).