Can 'なければなりません' be used for possibility?


I thought the use of this suffix was restricted to obligations, but the
sentence below has left me confused.

> この会に来たインドの人は「日本にいろいろ教えてもらって、早く空気をきれいにしなければなりません」と話していました。

Source: <http://www3.nhk.or.jp/news/easy/k10010874151000/k10010874151000.html>




This しなければなりません just means "must", "need to", "have to". And that's the only
meaning of しなければなりません.

> この会に来たインドの人は「日本にいろいろ教えてもらって、早く空気をきれいにしなければなりません」と話していました。
>
>   * An Indian person who came to the meeting said, "[I] have to make the air
> (of India) clean after Japan taught a lot of things to [me]."
>   * An Indian person who came to the meeting said, "[We Indian people] have
> to make the air (of India) clean after Japan taught a lot of things to
> [us]."
>

This person is probably someone in charge of the air pollution problem of
India, but since the subject is omitted, the second interpretation is
possible.

