1. The problem asks to identify which line segment is an altitude of triangle $\triangle CEG$. An altitude in a triangle is a line segment from a vertex perpendicular to the opposite side (or its extension). 2. From the graph description, line segment $GF$ is perpendicular to $EG$ (right angle marked between $GF$ and $FE$). Since $GF$ is perpendicular to $EG$, and $F$ lies inside the triangle, $GF$ is the altitude from vertex $G$ to side $CE$. 3. The other points $D$ and $F$ are on $CG$ and inside the triangle respectively, but no other perpendicular segments are indicated. 4. Therefore, the altitude is the line segment $GF$. Final answer: The altitude of $\triangle CEG$ is the line segment $GF$.