Who does the speaker not know in Chicago?

The speaker selects the option indicating that they do not know anyone in Chicago, which emphasizes a complete lack of familiarity with the city's inhabitants. This choice implies experiencing isolation or being new to an area where they have yet to form any personal connections.

The context of the other options illustrates different degrees of acquaintance. Saying "everyone" suggests a very broad knowledge of individuals, which contrasts sharply with the idea of knowing no one at all. Choosing "some friends" and "a colleague" indicates specific relationships that the speaker has, yet these options can't be correct since they imply some level of acquaintance. Thus, the choice that affirms the absence of any known individuals aligns perfectly with the idea of unfamiliarity that the question conveys.