Answer: A.a sound of thunder
A Sound of Thunder is a science fiction short story by Ray Bradbury. The story presents a future in which time travel is possible. A man buys a hunting trip with a company, which promises to take him to the past to hunt dinasours. However, the travellers need to make sure nothing in the past is altered.
When they arrive, the hunter accidentally steps on a butterfly. As they return to the present, he realizes that this small event has changed the nature of the present forever.
