9. Events A and B occur simultaneously on the x-axis of your reference frame. A occurred at x = +200 m and B at x = +1000 m. Which observer (there might be more than one, or even none) could possibly claim that A occurs before B:

(a) one moving relative to you in the negative x-direction,

(b) one moving relative to you in the positive x-direction,

(c) one moving relative to you in the positive y-direction, or

(d) none of these could observe A before B?