#### Answer

Vertex D, vertex G, and vertex I are adjacent to vertex F.

#### Work Step by Step

Two vertices are adjacent if there is an edge which connects the two vertices.
There is an edge which connects vertex D and vertex F, so vertex D is adjacent to vertex F.
There is an edge which connects vertex G and vertex F, so vertex G is adjacent to vertex F.
There is an edge which connects vertex I and vertex F, so vertex I is adjacent to vertex F.
Vertex D, vertex G, and vertex I are adjacent to vertex F.