Explanation:

- The passage talks about noise pollution and its effect on humans and the environment.

- Option 1, "other": This would not fit well because it suggests referring to multiple pollutions without a new category or singular term.

- Option 2, "another": This fits correctly as it indicates that noise pollution is an additional issue among other types of pollution.

- Option 3, "once": This doesn’t make sense in the context; it’s a temporal marker and doesn’t describe a category of issue.

- Option 4, "one's": This denotes possession and doesn’t fit the context of introducing another type of pollution.