With an angle of zero degrees, I assume that you mean that you are dealing with horizontal motion - that being motion only along the $x$ axis - with no vertical movement up or down. Maybe this is a cart on wheels, or the like, which you have pushed sideways. If there is no friction or other horizontal forces involved, then I agree with you that there will be no acceleration influencing this motion. That means that a kinematic motion equation like $x=x_0+ut+\frac12at^2$ would reduce to $x=ut$ (we place our coordinate system such that $x_0=0$), and then you have your formula $u=x/t$. I agree fully with all this.
The question now is, what does the term range refer to?
In mathematics, this term range refers to the set of all function values that are possible to get from a function. Meaning, "all possible outputs", so to say, which also sometimes is refered to as the image of a function.
I am guessing from your text that maybe we are supposed to imagine an elevation function (a $y$ function) that outputs $y$ values. Then the range would be all $y$ values that are possible to reach. If your motion is purely along the $x$ axis, as discussed above, then there is no change in the $y$ coordinate. If the motion starts at the origin where $y=0$, then the range would indeed be $0$ (since this is the only $y$ value that is possible to achieve).
This is guess-work, though, since it all depends on in what context this word range is used. So, have a check in your textbook (or ask the teacher who said this) for where this term is defined more accurately, or simply check for which exact function they are refering to when using the term range.