Which is considered an outlier?

Question

x:1,2,3,4,5,6,7,8,9 y:0.8,2.1,3.1,3.8,5.2,8.4,6.9,8.1,9

(2,2.1)
(4, 3.8)
(6, 8.4)
(9.9)

Can someone help, I think it's C or D?

Answer 1

I think C is farther out than D.