It’s so funny that all of the given choices all point to yes so I guess there is no choice for those who would like to answer this question but to say yes. You can answer any of the choices but the conviction of how you say it will be a bit different.

Letter A can still be perceived as not being sure. B comes with conviction so you definitely believe the statement. C can be the type of answer that you will say when you want to appease the person who is asking the question. D is the type of answer that you can use when you have a deeper understanding of the whole situation.