How do you calculate the Euclidean distance between two points?

a) |x1 - x2| + |y1 - y2|
b) √(x2 - x1)² + (y2 - y1)²
c) (x2 - x1)² + (y2 - y1)²
d) √|x1 - x2| + |y1 - y2|