How long is the segment line between the following points?

a) [[$ (5, 5)$]] and [[$(4, 5) $]]


b) [[$(-4, 2)$]] and [[$(-9, 2)$]]


c) [[$(1, -4)$]] and [[$(1, 8)$]]


d) [[$(-3, -7)$]] and [[$ (-3, 0)$]]