Answer:
A. It is a function because the input can be either 1 or 2 items, but the output
will always be the same price.
Step by Step Explanation :
A function is for every single input but the output is always the same. So, let's make a scenario. If someone bought ' 1 ' then paid the marked cost and if you bought 2 then paid the marked cost BUT with " One Buy One Free. " So, it is in fact a function.