Ok, I've seen the solution on Physics GRE.net, but I don't get it.
If I draw a spacetime diagram, the slope of a lightlike line is 1, and x=ct, right?
So to have a spacelike line, I need my slope to be bigger than 1; I need (ct)/x > 1. But this implies that (x/t)< c, which would be answer B, which is not correct!!!
What am I not getting here??