Explanation:

To determine the number in place of the question mark, we should check the given sequence: 68, ?, 407, 470, 496, 503. Let's analyze the differences between consecutive numbers to find a pattern:

- Find the difference:

- 470 - 407 = 63

- 496 - 470 = 26

- 503 - 496 = 7

- Considering the differences are decreasing:

- Check the first term 68 and potential numbers for the second position.

- Calculate backwards from the third term 407:

- Possible difference pattern could be reducing by factors:

- 407 needs a number when added to a smaller decreasing difference:

- Assume second difference option from known numbers:

- 407 - ? = difference in pattern

- If decreasing factor increases can be model:

- Need second number 283

- Verify Option:

- 283 is the number that continues the reduction:

- 407 - 283 = 124

- Further connects reduction pattern.

- Conclusion:

- Option 1: 283 fits the sequence pattern reducing by decrements.