This question is very oddly worded. The domain is the set of x-values, but this is a set of (x,y) ordered pairs.
I'm reading this question as "Here's a function, { (1,5), (2,1), (-1,-7) }. If this is reflected over the x-axis, what's the range?"
Assuming that is the question that is meant to be asked, reflecting a function over the x-axis will just change the signs of the y-values.
(1,5) -> (1,–5)
(2,1) -> (2,–1)
(-1,-7) -> (-1,+7)
I'd pick the third option.
