The chart below lists the original and sale prices of items at a clothing store. Clothing Prices
Original price Sale price
$7.99
$5.59
$10.99
$7.69
$12.99
$9.09
$15.99
$11.19
$24.99
$17.49
$29.99
$20.99
Which statement best describes why the sale price is a function of the original price?
As the original price increases, the sale price also increases.
The sale price is always less than the original price.
For every original price, there is exactly one sale price.
The sales price is never less than zero.

C) For every original price, there is exactly one sale price.

For any function, we always have any input go to exactly one output. The original price is the input while the output is the sale price. If we had an original price of say $100, and two sale prices of $90 and $80, then the question would be "which is the true sale price?" and it would be ambiguous. This is one example of how useful it is to have one output for any input. The input in question must be in the domain.

As the table shows, we do not have any repeated original prices leading to different sale prices.

a. is correct