Answer:
A) lump-sum salary increase.
Explanation:
Since in the question it is mentioned that Sally earned an increase of 10% in her salary and received an overall rise at the starting of the year in case that she do not leave the company.
Now after five months she quit a job, work for a competitor due to which she had to pay back the 10% payment as she break the rule of increase in lump sum salary
Therefore the correct option is A.