1. **State the problem:** We need to identify which line segment is a median of triangle $\triangle RTU$. 2. **Recall the definition of a median:** A median of a triangle is a line segment joining a vertex to the midpoint of the opposite side. 3. **Analyze the given points:** - $S$ lies on line segment $RT$. - $V$ lies on line segment $RU$. 4. **Check if $S$ is the midpoint of $RT$:** Since $S$ is on $RT$ and there are tick marks indicating equal segments on $RS$ and $ST$, $S$ is the midpoint of $RT$. 5. **Check if $V$ is the midpoint of $RU$:** The tick marks on $RV$ and $VU$ indicate $V$ is the midpoint of $RU$. 6. **Identify medians:** - The segment from vertex $U$ to midpoint $S$ on $RT$ is $US$. - The segment from vertex $T$ to midpoint $V$ on $RU$ is $TV$. 7. **Conclusion:** The line segments $US$ and $TV$ are medians of $\triangle RTU$. Since the question asks which line segment is a median, and the segment $SV$ is drawn inside the triangle but does not connect a vertex to the midpoint of the opposite side, $SV$ is not a median. **Final answer:** The medians are $US$ and $TV$.