Answer:
A). Which countries in the world have French as their first language?
Step-by-step explanation:
The question regarding 'the countries having French as their first language' would be most helpful for Chen to assess the scope of the career choice of the French translator. The key reason is that if the majority of the countries have French as their first language, his career scope and earning opportunities would become very narrow, and if the case is vice-versa, the scope would be quite wide. It would help him foresee the future of his career and make his decisions accordingly. Thus, option A is the correct answer.