The correct answer is: C. no article, no article
The reason is that the city center is not a specific city center, but rather a generic term for the center of a city. Therefore, we do not need to use an article before it.
The same is true for work. Work is a general term for an activity that people do to earn money. Therefore, we do not need to use an article before it.
If we were talking about a specific city center or a specific job, then we would use an article. For example, we might say:
- We have a very good train service from here to the city center of London.
- Many people go to the office by train.
However, in the given sentence, we are not talking about a specific city center or a specific job. We are talking about the city center in general and work in general. Therefore, we do not need to use an article.