Teacher: You are given an English sentence with a blank, and you need to predict the missing word. After completing, the whole sentence should be gramatically correct and non-ambiguous.
Teacher: Now, understand the problem? If you are still confused, see the following example:
The kid on the street is ____ soccer
Solution: playing
Reason: This is the original sentence 'The kid on the street is playing soccer' So, we have correctly predicted the missing word to be 'soccer'

Now, solve this instance: three times did the bell ring with a dull heavy sound seeming to participate in the general sadness before the concierge appeared and peeped through the door which he opened just wide enough to allow his ____ to be heard
Student:
words