Answer:
(-∞, ∞)
Explanation:
f circle g (x) is another way of expressing f(g(x)). Basically, we have to plug g(x) into f(x) wherever we see x's.
f(x) = x^2 - 1
f(x) = (2x-3)^2 - 1
Now find the domain. I think the easiest way to do this is to graph it. I've attached the graph. You can also do it algebraically by thinking about it: it's a positive parabola (+x^2) and its minimum is -1, so its range will not be all real numbers, but its domain will certainly be. (The range would be answer choice B!)
Domain = (-∞, ∞)