An analyst at a paper company made the table below of the sales by month at his company.

month 1 2 3 4 5 6 7 8 9 10 11 12

units sold
(in thousands) 24 29 53 35 24 56 81 81 74 74 76 11

which of the following does his data represent?
a.
both a relation and a function
b.
a function only
c.
neither a relation nor a function
d.
a relation only