How does the author use foreshadowing in Tunnel in the Sky?

Tunnel in the Sky is a novel by science fiction writer Robert A. Heinlein. In this novel, Rod Walker is taking a survival course required for his ambition to be an Outlands professional. The final exam has arrived, requiring Rod to be placed on an unknown planet and forced to survive either alone or with one team member for four to ten days. Rod is apprehensive, especially in light of some turmoil at home, but is eager to prove he can survive. However, four to ten days quickly turns into weeks, then months, then years. Tunnel in the Sky is an exciting look at what happens to young people when all modern convenience disappears overnight, making man the greatest danger, as well as the greatest asset, a young man can face.