Concept:An error affects the trial balance only when it makes total debits unequal to total credits.
Explanation:A compensating error cancels itself out with another error.
Its net effect on the totals is zero.
So it does not affect the trial balance totals.
A complete reversal of entry records equal amounts on both sides.
The totals of debits and credits remain equal.
So it does not affect the trial balance totals.
An error of original entry also keeps debits and credits equal.
So it does not affect the trial balance totals.
An error in addition incorrectly changes the total of one column.
This makes total debits differ from total credits.
Therefore, only an error in addition affects the totals of a trial balance.
Answer:C. error in addition