Final answer:
The Social Security taxes for the year 2015 were calculated based on a wage base limit of $118,500, which is the correct answer, option C.
Step-by-step explanation:
Social Security taxes are calculated on a base wage limit that is adjusted each year for inflation. For the year 2015, the wage base limit for Social Security taxes was set at $118,500. This wage base limit refers to the maximum amount of earned income upon which a worker pays Social Security taxes at a rate of 12.4%, which is split evenly between the employer and the employee at 6.2% each.
Any earned income above this threshold is not subject to Social Security taxes. The Medicare tax, however, is assessed at 1.45% of gross income with no upper limit. Therefore, the correct answer to the student's question is C) $118,500.