Which of the following real-world objects is the best model for a line segment?

A straight train track extending to the horizon

The straight edge of a rectangular table

What is the primary difference between the notation for ray $\overrightarrow{XY}$ and ray $\overrightarrow{YX}$?

They represent the same ray but are written differently.

$\overrightarrow{XY}$ starts at point X, while $\overrightarrow{YX}$ starts at point Y.

$\overrightarrow{XY}$ is shorter than $\overrightarrow{YX}$.

One is a ray and the other is a line segment.