Read the passage.

Former astronaut Scott Kelly spent a year on the International Space Station. Scott has a twin brother named Mark, who was also an astronaut. Scott and Mark participated in experiments that compared their health while Scott was in space and Mark was on Earth.

Based on the information provided, what visual information would be most helpful to include with the passage?

a time line of all space missions
a photograph of two astronauts in space
a graph comparing the health results of the experiment
a chart listing all astronauts visiting the International Space Station