In a Situation Where an Object Can Move Only Along $x$

Short Answer

In a situation where an object can move only along the $x$ axis, you see this statement in a book: "The object's velocity is $\mathrm{v}=\left(x-x_{0}\right) / t$ , where $x$ is the object's position at time $t$ to the left or right of its position $x_{0}$ at time $t=0$ ." Is $v$ being used here as a shorthand for $|\vec{v}|(\mathrm{A})$ or $v_{x}(\mathrm{C})$ ?
$\bullet$ A
$\bullet$ C