Answer:
(c) √65
Explanation:
If you draw a line segment between the points, you can see that it makes a triangle with the grid lines. The segment you drew is the hypotenuse of a right triangle that is 1 unit wide and 8 units high. The Pythagorean theorem tells you the length of that hypotenuse is ...
length = √(1² +8²) = √(1 +64)
length = √65