Answer:
B.) 10
Step-by-step explanation:
You could use the distance formula to calculate the length of AB, I prefer a visual approach, because it requires less memorization.
Draw a vertical line from B and a horizontal line from A until they intersect at D (5, 4).
Then you have a right triangle ABD, and you can use Pythagoras' theorem to calculate AB.
[tex]\begin{array}{rcl}AB^{2} & = & AD^{2} + BD^{2}\\& = & 8^{2} + 6^{2}\\ & = & 64 + 36\\& = & 100\\AB& = & \sqrt{100}\\&= & \mathbf{10}\\\end{array}[/tex]
