Answer
Graph(a)
Work Step by Step
Given: $r(t)=ti$ and $-1 \lt t \lt 1$
This represents any point on the graph having the form of $(t,0,0)$ .
Here,the $y$ and $z$ intercepts are both $0$. The value of $x$ is in between $-1$ to $+1$ which makes a line segment along $x$-axis.
The answer is: Graph(a).