To determine which of these examples has an addition error, we need to verify if the sum given for each option is correct. Here are the results:
1. Option A:
[tex]\[
13,246 + 84,631 = 97,877
\][/tex]
This sum evaluates correctly, so there is no error here.
2. Option B:
[tex]\[
52,634 + 25,145 = 77,779
\][/tex]
This sum evaluates correctly, so there is no error here.
3. Option C:
[tex]\[
38,273 + 51,425 = 89,798
\][/tex]
This sum does not evaluate correctly. Instead of 89,798, the correct sum is 89,698. This shows a mistake where the given result is off by one.
4. Option D:
[tex]\[
46,371 + 32,618 = 78,989
\][/tex]
This sum evaluates correctly, so there is no error here.
Thus, the option with an error of addition by one is C: [tex]\(38,273 + 51,425 = 89,798\)[/tex].