It's hard to tell what the options are lol, but I'd say Mysterious.
The narrator hears tapping -- neither he nor the reader knows what it is. The core of the word mysterious is <em>mystery</em>, and this provokes a question our minds; what could it be?
Answer:
shifts
Explanation: shift means when you move something from a place to another. Changes is the closest to that word.
Running a race is as hard as a cat trying to speak English.
