Explanation:

 b)Registration of births and deaths. Since its the other function of the office of the registrar general and census commissioner, it’s important that you know it. In this question, even if you didn’t know the answer, you could apply your knowledge of current affairs. In India, we do not have a uniform civil code. This matter keeps coming up in the newspapers, and we read articles about minorities having their separate personal laws. So, if that is the case, how can the registrar general register marriages? That eliminates option a and c.