On the number line, if \(r < s,\) if \(p\) is halfway between \(r\) and \(s,\) and if \(t\) is halfway between \(p\) and \(r,\) then \(\dfrac{s – t}{t – r}=\)

(A) 1/4
(B) 1/3
(C) 4/3
(D) 3
(E) 4

[spoiler]OA=D[/spoiler]

Source: Official Guide