1) x is definitive not within the circle as it exceeds the readius

I fully agree with your assessment of 1)

2) y can be 9" away from x in any direction

Again, I fully agree...

Now taking them together, X is just outside the circle. Y can't lie inside the circle because 9 is 4.5 past the centre of the circle. Also note that Y creates another radius around X. If you draw these two circles, they never overlap.

Thus C

Individually: both insufficient

Togethor: we can definitively say that y can never be in the circle since if X is .5 outside the circle in the circular plane and the distance between x and y is 9 than y itself must be .5 outside the circle since the diameter is 8.

hope this helps.