Answer:
option A
Step-by-stevvp explanation:
In the formula
The formula is used to find the distance between two points
(x2-x1) gives the length of one leg
(y2-y1) gives the length of another leg
In a right angle triangle , Pythagorean theorem is 
where a and b represents the sides of the triangle
Each subtraction expression in the formula represents the leg of the right angle triangle with the hypotenuse of length d