Final answer:
The narrator pressed down on the accelerator in 'The Hitchhiker' by Roald Dahl because they felt threatened by the hitchhiker.
Step-by-step explanation:
The narrator pressed down on the accelerator in 'The Hitchhiker' by Roald Dahl because the narrator felt threatened by the hitchhiker. In the story, the hitchhiker displays increasingly suspicious behavior, which makes the narrator uneasy. By pressing down on the accelerator, the narrator tries to create distance between themselves and the hitchhiker in order to protect themselves.