No improvement to this sentence is necessary. It makes perfect sense on its own and sounds right. "Either" always takes an "or" else the word wouldn't make sense, as it's meant to contrast binary options.
eg.
I'm either going to eat food or drink water.
Answer:
i think it is personification...
Explanation:
the sentence says, "a steady tapping *reached* otis's ears"
To make sure that the teacher can understand your paragraphs is what she means. Hope this helps! ;)