Answer: 8.9 units (choice C)
Explanation:
We plug [tex](x_1,y_1) = (7,-1) \text{ and } (x_2,y_2) = (-1,3)\\\\[/tex] into the distance formula to get the following
[tex]d = \sqrt{(x_1 - x_2)^2 + (y_1 - y_2)^2}\\\\d = \sqrt{(7-(-1))^2 + (-1-3)^2}\\\\d = \sqrt{(7+1)^2 + (-1-3)^2}\\\\d = \sqrt{(8)^2 + (-4)^2}\\\\d = \sqrt{64 + 16}\\\\d = \sqrt{80}\\\\d \approx 8.94427\\\\d \approx 8.9\\\\[/tex]