Which language proficiency question is appropriate to ask in an interview?

Asking about fluency in specific languages is the most appropriate way to assess a candidate's language proficiency in an interview. This question directly targets the candidate's ability to communicate effectively in those languages, which is crucial for roles requiring language skills. Fluency encompasses not just the ability to speak but also to understand, read, and write in the language, thus providing a comprehensive view of the candidate's capabilities.

Other options may not provide a clear or complete assessment of language skills. For instance, asking about preferences or the number of languages a candidate can translate may not indicate their level of proficiency or practical communication skills. Additionally, inquiring if someone speaks English "well" is subjective and can lead to ambiguous interpretations, as the term "well" can mean different things to different people. The focus on fluency in specific languages ensures the interviewer obtains clear and relevant information regarding the candidate's abilities in the context of the role.