Are "to, two and too" your suggested possibilities to complete the sentence? If so, it would have to be something like:
"…three 'to'-sounding homophones in the English language."
…but that is not the given sentence.
The only possibility is:
There are three e's in the English language. (That is: in "thE English languagE"
However, this is incorrect, because of the punctuation.
He was a big star in the 1980s. (No apostrophe before the 's')
"There are three 'e's in the English language." (Here, it is necessary to enclose the 'e' in quotes to distinguish that we mean the letter 'e' from "…three es in the…"