Set \(T\) consists of all points \((x,y)\) such that \(x^2+y^2 =1.\) If point \((a,b)\) is selected from set \(T\) at random, what is the probability that \(b>a+1?\)

A. 1/4
B. 1/3
C. 1/2
D 3/5
E. 2/3

[spoiler]OA=A[/spoiler]

Source: GMAT Club Tests