Final answer:
Option a, Nadia, who speaks French, Spanish, and English, is the correct example of being multilingual, as it refers to speaking multiple languages.
Step-by-step explanation:
The example of being multilingual among the options provided is a. Nadia, who is Spanish, speaks French, Spanish, and English. Being multilingual means being able to speak and understand multiple languages.
In Nadia's case, she speaks three different languages, which qualifies as multilingual. The other options present cases of code-switching, cultural fluency, and understanding of social nuances within a single language and hence do not align with the definition of multilingualism.
Individuals or characters in those examples may be skilled in social or cultural adaptation but are not necessarily multilingual as they do not demonstrate fluency in more than one language.